INTRODUCTION

Latah County covers approximately 1080 mi2 in northern Idaho. The geology of the county is very diverse and complex. From oldest to youngest, the rock types are the metamorphic rocks of the Belt Supergroup, intrusive rocks of the Idaho Batholith, extrusive rocks of the Columbia River Basalts, and sedimentary deposits. The catalyst for this project came from a mineralogy class I took as an

undergraduate. One of the requirements for completing the course was to collect and identify at least 25 minerals from the county. The first question that came to mind was "where do I go to find these minerals?"

The first part of this project consisted of extensive field work in Latah County. The primary emphasis was on abandoned mining areas, numerous basalt quarries, and various outcrops along the highways, county roads, and Forest Service roads. Hand samples of the minerals, or the rocks containing visible minerals, were collected at each site. The minerals collected and identified at the various locations were limited to those clearly visible with the naked eye or with the aid of a hand lens.

The second part of the project consisted of laboratory studies using a petrographic microscope, X-ray diffractometer, and the scanning electron microscope to identify positively the individual minerals.

It was not the purpose of this project to identify all the minerals in Latah County. Many minerals other than those included in this thesis exist, and it would require a lifetime of work to locate all of them. Hopefully, this project will inspire further studies, and be a valuable educational tool and a source of enjoyment for science teachers, students, and the general public.

The thesis provides a brief introduction to the geology of Latah County, followed by 18 mineral-collecting localitites. Each of the 18 localitites stands alone with a brief geologic setting, road log, location map, and mineral descriptions. Individual descriptions are provided for each location because mineral appearances, such as forms, habits, and colors may vary owing to subtle structural properties. Because each section is self-contained, each can be "Xeroxed" and taken into the field.

Certain mineral associations occur together because rocks are merely associations of minerals. For instance, basalt, a dark-colored, fine-grained rock is comprised of such primary minerals as Ca-rich plagioclase, olivine and augite. Secondary minerals include calcite, aragonite, siderite, goethite, opal, or zeolite. Granite and syenite contain quartz, feldspar, and mica as primary minerals, and accessory minerals such as hornblende, actinolite, zircon, titanite, apatite, and magnetite. Metamorphic rocks will vary mineralogically depending on parent material and temperature and pressure conditions. The most common minerals are amphibole, pyroxene, muscovite, biotite, talc, serpentine, Ca-rich plagioclase, garnet, staurolite, kyanite, sillimanite, andalusite, and chlorite.

Two appendices are also included. Appendix A is a more thorough description of the local geology, and Appendix B lists the minerals and locations by mineral name.

GENERALIZED GEOLOGIC HISTORY

FOR LATAH COUNTY

Introduction Summary

Latah County is located on the eastern edge of the Columbia River Plateau, near the western slope of the Rocky Mountains. Major geologic units consist of Precambrian metasediments and metamorphics of the Belt Supergroup, Cretaceous-Tertiary intrusions and metamorphics of the Idaho Batholith, Miocene volcanics and sediments of the Columbia River Basalt Group and Pleistocene loess of the Palouse Formation (Figure 1). Lesser units include Cretaceous syenite near Potlatch, Eocene rhyolite and breccias generally restricted to the Deary-Bovill area (Figure 1), and sedimentary interbeds associated with the Columbia River Basalt Group in the Troy-Bovill area.

Precambrian rocks of the Belt Supergroup generally exhibit features associated with low-grade regional metamorphism, and consist mostly of quartzite, argillite, and siltite. Outcrops contain relict cross-beds, ripple marks, bedding laminations, and other sedimentary features. However, at numerous localities, the Belt rocks are metamorphosed to phyllite, schist, and gneiss and the sedimentary features are destroyed. These Precambrian units, along with Mesozoic intrusions, form most of the topographic highs in the Moscow area. Exceptions could be Kamiak and associated buttes. Kamiak Butte consists of coarse-grained, recrystallized quartzite. Savage (1973) considered the Kamiak quartzite to be a Precambrian, coarse-grained equivalent of Belt Supergroup rocks. However, Hooper and Webster (1982) tentatively correlated the quartzite in the Moscow-Pullman area with similar Cambrian quartzite of northeast Washington.

Intrusive rocks in the Moscow area belong primarily to the Cretaceous-Tertiary aged Idaho Batholith and commonly range in composition from quartz monzonite to granite and quartz diorite. Local outcrops of tonalite, gabbro, and syenite are common. The Palouse Range, which rims Moscow to the north and northeast, consists of undifferentiated Idaho Batholith rocks. Bald Butte, three miles southwest of Moscow, consists of quartz-rich tonalite devoid of alkali feldspar (Hooper and Webster, 1982).

Accompanying and following emplacement of the Idaho Batholith was a period of extensive erosion. Near Moscow, the pre-basalt relief was considerable, whereas to the west the relief was less and a broad, flat plain may have existed. The lower areas were filled by the basalt that erupted from vents during an 11 million year period in the Miocene between 17 million and 6 million years ago (Hooper, 1982). These flows belong to the Columbia River Basalt Group which filled local canyons and flowed primarily westward into a rapidly subsiding basin that existed over the present Tri-Cities area. Along the edges of the plateau, lava dams formed across canyons; lake sedimentation occurred, and preservation of plant fossils was common. The fossils indicate that the climate was slightly warmer and more humid during the extrusion of the lava flows.

Beneath Moscow, the Columbia River Basalt Group is approximately 1,300 feet thick and represents a filled paleo-valley between the Palouse Range to the north and Paradise Ridge to the south. In general, the rocks beneath Moscow consist of three thick sediment sequences alternating with the basalt flows.

At least 95 percent of the enormous volume of Columbia River Basalt accumulated in the first 3.5 million years (Hooper, 1982), and after this eruptive event the major drainages of the nearby Snake and Clearwater began to re-establish themselves. In addition to influence from continuing sporadic volcanism, the river courses were also influenced by deformation. In the Moscow area, this deformation is best expressed along the Snake and Clearwater Rivers in the Lewiston vicinity, where two major east-west structures dominate. One structure, the Lewiston Basin, is approximately 21 miles long; and its axis is located just south of Lewiston and Clarkston, paralleling the Lewiston Basin in a complex, asymmetric and faulted east-west anticline, referred to as the Lewiston structure and was mapped in detail by Camp (1976). The basalts directly beneath Moscow are considered to be primarily horizontal with a slight westerly dip.

Pleistocene loess of the Palouse Formation mantles the bedrock in the Moscow area. The sources for this wind-blown soil have been debated a great deal in recent years.

Approximately 6,700 years ago, Mt. Mazama, one of the Cascade volcanoes, erupted; and ash was deposited over much of the northwest. The center of the volcano was Crater Lake, Oregon, and the ash that was deposited is referred to as the Mazama Ash. There is evidence of earlier ash deposits in this area associated with other explosive Cascade volcanoes, but none are as extensive as the Mazama Ash. Most recently, Mt. St. Helens, in 1980, was responsible for the deposition of a very thin layer of ash in the Moscow area.

Figure 1: Rock units and numerical display of locations

coinciding with alphabetical order in the paper

(modified from Tullis, 1944).

MINERALS OF LATAH COUNTY

Individual Locations

The following sections consist of 18 individual mineral collecting locations. The information for each location contains the legal description, ownership, and an abbreviated description of the general geology at each site. A road log with a coinciding map, and an alphabetized list of the minerals present with detailed descriptions of each mineral are also included for each location.

The individual sites are arranged alphabetically for the sake of simplicity. Hopefully, others will use this thesis as a reference guide. An alphabetized list of the 56 minerals described in the thesis, along with where they can be found, is available in Appendix B.

BASALT QUARRY

ON PALOUSE RIVER

NEAR POTLATCH, IDAHO

Legal Description: Ownership:

SE1/4, NE1/4, NW1/4, Sec 10, T41N, R5W Bennett Lumber

Latah County, Idaho Products Incorporated

Potlatch Quadrangle, Idaho P.O. Box 49

7.5 Minute Series (Topographic) Princeton ID 83857

Latah County Map Series Phone: (208) 875-1121

The basalt quarry is located approximately 15 miles north of Moscow, along Highway 95, on the left hand side of the road (Figure 2). The Palouse River is on the north side of the quarry. The 70 to 80 feet thick outcrop is a Priest Rapids Member, of the Wanapum Formation, of the Columbia River Basalt.

Road Log: (refer to Figure 2)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on Highway 95 towards

Potlatch.

14.8 Turn left on gravel road; the quarry is approximately 50 yards

straight ahead.

This location is a good place to take students of any grade level. It is easily accessible during all seasons. The Latah County map code is 1.

Figure 2: Map to basalt quarry on the Palouse River near Potlatch, Idaho.

Minerals Present:

Aragonite Limonite

Calcite Opal

Goethite Siderite

Hematite

Mineral Appearances:

Aragonite - CaCO3 (Calcium Carbonate)

Aragonite occurs as small, acicular (needle-like), radiating

crystals within the vugs of the basalt. These elongated prismatic crystals are semi-hard (3.5 - 4.0) and very fragile with a vitreous luster, a white streak, and a brownish-yellow to white color.

Calcite - CaCO3 (Calcium Carbonate)

Calcite occurs as small, compact, yellowish-white, marble-like masses filling the vugs in the basalt. It has a hardness of 3.0 with a vitreous to pearly luster and a white streak. These properties along with brisk effervescence in cold hydrochloric acid make calcite relatively easy to identify.

Goethite - [[alpha]]-FeOOH (Iron Hydroxide)

Goethite is present in the form of botryoidal brownish-black aggregates. It can be distinguished from siderite by its higher degree of hardness (5.0 - 5.5) dark brown to black color, and brownish-yellow streak. Goethite also occurs as a thin, brown, poorly crystalline coating over the botryoidal siderite. X-ray diffraction analysis verified the identification.

Hematite - Fe2O3 (Iron Oxide)

Hematite occurs as compact, granular masses. It is relatively hard (5.5 - 6.5), has a high specific gravity, exhibits no cleavage, has an earthy luster, produces a red-brown streak, and is a deep red color.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the basalt. The physical properties of limonite are highly variable owing to varying chemical composition and habit, but at this location it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and is very fragile.

Opal - SiO2*nH2O (Hydrous Silicon Oxide)

The white or clear opal is present as botryoidal, globular masses encrusting the basalt, as well as being present within the vugs in the basalt.

The differences in color of the opal samples may be due to varying impurities in the specimens. Opal is relatively easy to identify. It has a hardness of 5.5 - 6.5, low specific gravity, and a vitreous or greasy luster. It is also fragile, with very small conchoidal fractures present in nearly all of the samples.

Siderite - FeCO3 (Iron Carbonate)

Siderite is present as botryoidal globular masses within the vugs in the basalt. It has a hardness of 3.5 - 4.0 with a bright vitreous luster and a white streak. The color varies from a very pale brown to a pale yellow or white. The spheres are thinly coated with brown goethite and range in size from 1 to 5 mm. Identification of this mineral was verified by the use of X-ray diffraction in the laboratory.

EMERALD CREEK

GARNET SITE

Emerald Creek Garnet Co.

Legal Description: Ownership:

SW1/4, NW1/4, Sec. 34, T43N, R1E, & Emerald Creek Garnet Co.

SE1/4, SE1/4, Sec. 33, T43N, R1E P. O. Box 190

Benewah & Shoshone County, Idaho Fernwood ID 83830

Clarkia Quadrangle, Idaho Phone: (208) 245-2797

7.5 Minute Series (Topographic) (208) 245-2096

Latah County Map Series

"The Emerald Creek Garnet Area"

Legal Description: Ownership:

NE1/4, NE1/4, SW1/4, U.S. Government

Sec. 6, T42N, R1E St. Maries Ranger District

Latah County, Idaho P.O. Box 407

Fernwood Quadrangle, Idaho St. Maries ID 83861

7.5 Minute Series (Topographic) Phone: (208) 245-2531

Latah County Map Series

The Emerald Creek Garnet Company mining site is located approximately 3.5 miles west-northwest of Clarkia, Idaho on or near the Benewah-Shoshone County line. However, the garnet and other minerals present at this location originated in the mica schist and other metamorphic rocks from Emerald Creek drainage area in northeastern Latah County and therefore, it seems appropriate to include it as a Latah County location. The road log includes directions to two separate sites (Figure 3). The first location is to the Emerald Creek Garnet Co. mining site off of State Highway 3. The second location is on U.S. Forest Service property and is known as "The Emerald Creek Garnet Area." This site is within Latah County on St. Joe National Forest property.

Road Log: (refer to Figure 3)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 through Troy,

and Deary to Bovill.

32.7 Turn left on State Highway 3 at Bovill and proceed north through Clarkia towards St. Maries.

51.8 Turn left (south) on Forest Service Road #447. The Emerald Creek Garnet Co. processing plant is to the right.

Proceed south on FSR #447.

54.9 Stop #1 The mining site and tailings piles are adjacent to

the road. Continue on FSR #447 to "The Emerald Creek Garnet Area." It is important to obtain permission from the owners

before going on the property.

59.8 Stop #2 Parking area. An information center and the digging

areas are a 0.5 mile hike up 281 Gulch.

This location is open to the public from Memorial Day weekend through Labor Day weekend, seven days a week from 8:00 a.m. to 5:00 p.m. Permits are availabe from the information center at the digging site. The Emerald Creek Garnet Area is one of two places in the world where the dodcecahedral star garnet crystals are found. They range in size from as small as 0.5 cm to as large as 3 or 4 cm in diameter and commonly have four or six ray stars. These gem quality garnets are generally found in the gravel and sand above the metamorphic bedrock or within the mica schist.

Figure 3: Map to Emerald Creek garnet mining site and Forest Service garnet area northwest of Clarkia.

This is an excellent location for students of all ages. It is easily accessible, and the owners are willing to allow groups to visit the site. The Latah County map code is 2.

Minerals Present:

Biotite Muscovite

Garnet (Almandine) Quartz

Kyanite Sillimanite

Mineral Appearances:

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 3 mm across and are the main constituent of the mica schist. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish- black color.

Garnet (Almandine) - Fe3Al2(SiO4)3 (Iron Aluminum Silicate)

The garnets along this route are contained in the mica schist. They are relatively small, ranging in size from <1 mm to 3 mm in diameter. Some of these garnets display a prominent dodecahedral shape but most are in the form of rounded grains. Garnets are hard (6.5 - 7.5) and lack cleavage. Uneven or subconchoidal fractures are common along with an adamantine luster, a white streak, and a dark red-brown color. Identification of this mineral was verified by using the X-ray diffractometer in the laboratory.

Kyanite - Al2SiO5 (Aluminum Silicate)

Kyanite is present in the form of elongated tabular crystals ranging in size from 0.5 to 2 cm long and approximately 0.5 cm wide. This mineral is unique in that its hardness varies from 6.0 - 7.0 parallel to the cleavage planes to 4.0 - 5.0 across the cleavage planes. Kyanite has a vitreous to pearly luster, a white streak, and is commonly light blue or blue-gray in color. Positive identification was made by using the X-ray diffractometer in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite mica occurs as small (~ 5 mm), thin disseminated plates in the mica schist. These flexible, elastic plates exhibit perfect basal cleavage, prominent vitreous luster, and a silvery or yellowish-white color.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, compact, cryptocrystalline rocks in the tailings piles. It is present as a result of hydrothermal activity in the area. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage, but conchoidal fractures are evident, and has a vitreous luster.

Sillimanite - Al2SiO5 (Aluminum Silicate)

Sillimanite occurs as long, slender, fibrous crystals within the mica schist and in the loose material in the tailings piles. The crystals are 0.5 to 1.5 cm long and approximately 0.5 cm wide. They vary slightly in color from a yellowish-white to gray in the mica schist. The yellowish-white sillimanite present in veins has been weathered and is very fragile, but the crystals within the schist have a hardness of 6 - 7 with a vitreous or pearly luster and perfect cleavage parallel the the direction of elongation. Identification of this mineral was verified through the use of the X-ray diffractometer in the laboratory.

FOREST SERVICE ROAD #447

Legal Description: Ownership:

Sections 11, 12, & 13, T42N, R1W & U.S. Forest Service

Sections 8, 9, & 18, T42N, R1E St. Maries Ranger District

Latah County, Idaho P.O. Box 407

Clarkia, Fernwood, & Emida St. Maries ID 83861

Quadrangles, Idaho Phone: (208) 245-2531

7.5 Minute Series (Topographic)

Latah County Map Series

Road Log: Guide to various stops along FSR #447

(refer to Figure 4)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch, Princeton, and Harvard.

30.5 Turn right on Palouse River Road (to Laird Park & Camp Grizzly).

0.0 From junction of State 6 and Palouse River Road.

1.5 Pavement ends but well-kept gravel road continues.

1.8 Cross the bridge and turn left on Forest Service Road #447

6.7 Turn right on FSR #447 and cross the North Fork of the

Palouse River.

13.6 Cross-roads-FSR #447 and FSR #377.

14.9 Stop #1. Excellent metamorphic outcrop.

Actinolite Diopside Biotite

15.2 Stop #2. Another excellent metamorphic outcrop.

Scapolite Actinolite

17.2 Stop #3. Garnet schist

Garnet Muscovite

Sillimanite Biotite

18.3 Stop #4. Garnet schist. Garnets are smaller but more

plentiful than at stop 3.

20.5 Emerald Creek Campground.

22.1 Emerald Creek Garnet Co. mining site.

25.2 Junction of FSR #447 and State Highway 3.

Emerald Creek Garnet Co. processing plant is on the left.

Figure 4: Map along Forest Service Road #447 paralleling the

the East Fork of Emerald Creek.

This trip would be more interesting for university mineralogy and petrology classes. The different geological formations and phenonena, such as banding, folding, and contacts, and the associated minerals are easy to see and identifiy. The Latah County map code is 3.

Minerals Present:

Actinolite Garnet (Almandine)

Biotite Muscovite

Diopside Scapolite

Mineral Appearances:

Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2

(Hydrous Calcium Magnesium Iron Silicate)

Actinolite occurs as elongated prismatic crystals in the metamorphic rocks. The color ranges from a light to dark green, and the crystals exhibit perfect cleavage parallel to the elongation direction. Actinolite is hard (5.0 - 6.0), with a vitreous to silky luster. Actinolite also occurs in a fibrous form with the same physical properties. Positive identification was attained by the use of the X-ray diffractometer, and the Scanning Electron Microscope in the laboratory.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 3 mm across and are the main constituent of the mica schist. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish- black color.

Diopside - CaMgSi2O6 (Calcium Magnesium Silicate)

Diopside occurs as slightly elongated prismatic crystals, fibrous radiating aggregates, and granular masses in the metamorphic rocks. Diopside has a hardness of between 5.0 and 6.0 with two directions of cleavage at approximately 90deg.. The crystals display a vitreous luster, a white streak, and are dark green in color. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

Garnet (Almandine) - Fe3Al2(SiO4)3 (Iron Aluminum Silicate)

The garnets along this route are contained in the mica schist. They are relatively small, ranging in size from <1 mm to 3 mm in diameter. Some of these garnets display a prominent dodecahedral shape but most are in the form of rounded grains. Garnets are hard (6.5 -7.5) and lack cleavage. Uneven or subconchoidal fractures are common along with an adamantine luster, a white streak, and a dark red-brown color. Identification of this mineral was verified by using the X-ray diffractometer in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite mica occurs as small (~ 5 mm), thin disseminated plates in the mica schist. These flexible, elastic plates exhibit perfect basal cleavage, prominent vitreous luster, and a silvery or yellowish-white color.

Scapolite - (Na,Ca,K)4Al3(Al,Si)3Si16O24(Cl,SO4,CO3)

(Complex Silicate)

Scapolite ocurrs as microgranular masses or aggregates in and on the metamorphic rocks at this site. Some very small prismatic crystals can be seen with the aid of a hand lens. Scapolite has a hardness of 5.0 - 6.5, very poor cleavage, a dull vitreous luster, and is grayish-white in color. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

GEMMILL PROSPECT

Legal Description: Ownership:

E1/2, NW1/4, Sec15, T39N, R3W Bert Nelson

Latah County, Idaho 1041 Camps Canyon Road

Little Bear Ridge Quadrangle, Idaho Troy ID 83871

7.5 Minute Series (Topographic) Phone: Unavailable

Latah County Map Series

The Gemmill prospect is located east-southeast of Troy, Idaho. There are prospect shafts, pits, and cave adits for approximately 1/4 mile along the creek (Hubbard, 1957). These locations are upstream and downstream from where Camp's Canyon Road crosses Little Bear Creek (Figure 5). The rock types in this area are pre-Tertiary metamorphic formations exposed as the stream cut through the Columbia River Basalt which caps the region.

Road Log: (refer to Figure 5)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 through Troy.

11.6 From the east side of Troy; continue following Highway 8

towards Deary.

12.6 Turn right on Little Bear Ridge Road.

13.2 Turn right on Camp's Canyon Road.

15.7 Stop! Camp's Canyon Road crosses Little Bear Creek. The

shafts, pits, and adits are along the creek, both upstream

and downstream from the crossing. The first pit is on the left

side of the road immediately after the road crosses the creek.

The second site, a caved-in adit entrance, is located approximately 100 yards upstream (north) of the road and approximately 50 yards east of the creek. The adit is cut into

the side of a little ridge that dips towards the creek bed. The

third site is located downstream (south) of the road on the east side of the creek. There are abandoned buildings at this

site and numerous exploratory pits where minerals can be found. According to Hubbard (1957), there are several more

sites along the creek that would be interesting to investigate

but the mineralogy is similar at all locations.

Figure 5: Map to Gemmill prospect east of Troy, Idaho.

This location is excellent for students of all ages. It is easily accessible by automobile, and relatively level terrain makes for easy hiking between the adits and pits. There is a wide variety of minerals present, as well as examples of contact metamorphism and hydrothermal activity. The Latah County map code is 4.

Minerals Present:

Azurite Chalcopyrite Limonite

Biotite Native Copper Malachite

Bornite Garnet Pyrite

Calcite Labradorite Quartz

Mineral Appearances:

Azurite - Cu3(CO3)2(OH)2 (Hydrous Copper Carbonate)

Azurite occurs as very small, striated, tabular, prismatic, radiating, intergrown crystals in the rocks found in the hydrothermal veins, and as a granular film coating the copper-bearing metamorphic rocks. This secondary copper mineral is semi-hard (3.5 - 4.0), displays good cleavage with a vitreous luster, and has a pale blue streak. It is commonly associated with malachite.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 3 mm across and are found in the rocks in the hydrothermal veins. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish- black color.

Bornite - Cu5FeS4 (Copper Iron Sulfide)

Bornite can be found as octahedral crystals at this location, but it is more likely to be found as compact granular masses. It commonly displays a reddish-bronze color which is tarnished to an iridescent purple and blue film. The old miners referred to bornite as "Peacock Ore." Bornite has a hardness of 3.0, a high specific gravity, a gray-black streak, and a metallic luster.

Calcite - CaCO3 (Calcium Carbonate)

Calcite occurs as small, compact, yellowish-white, marble-like masses filling the fractures and coating the exterior of the metamorphic rocks. It has a hardness of 3.0 and a vitreous to pearly luster and a white streak. These properties, along with brisk effervescence in cold hydrochloric acid, make calcite relatively easy to identify.

Chalcopyrite - CuFeS2 (Copper Iron Sulfide)

Chalcopyrite occurs as compact granular masses as a result of hydrothermal activity and metamorphism. It has a hardness of 3.5 - 4.0, a high specific gravity, lacks cleavage, a greenish-black streak, and a semi-metallic luster. Chalcopyrite is dark, brassy yellow in color and is coated with an iridescent film.

Native Copper - Cu (Native Element)

Small amounts of copper are present as compact, filiform masses. It displays the characteristic copper-red color on fresh surfaces. However, most samples are coated with a greenish malachite film or a blackish or iridescent film. Copper is soft (2.5 - 3.0), very heavy, and malleable with a metallic luster.

Garnet - (Ca,Fe)3Al2(SiO4)3 (Calcium, Iron Aluminum Silicate)

The garnets at this location occur as grossular-andradite garnets. They are present in the rocks found in the hydrothermal veins and at the contact with the surrounding metamorphic rocks. The dodecahedral crystals are small (~ 1 mm across), very hard (6.5 - 7.5), have subconchoidal fractures, and a vitreous luster. Owing to the varying amounts of calcium and iron in the chemical composition, these garnets range in color from light green to pink to red, cinnamon or brownish-black. Positive identification was obtained by using the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Labradorite (plagioclase) - (Ca,Na)AlSi3O8

(Calcium, Sodium Aluminum Silicate)

The plagioclase feldspar present at this location is a solid solution between anorthite and albite end-members and contain equal amounts of calcium and sodium. The elongated, white to yellow-white crystals are small (~2 mm long and 0.5 mm across), and display a slight play on colors giving off an iridescent blue color. Plagioclase has a hardness of 6.0, a vitreous to pearly luster, nearly perfect 90deg. cleavage, and striations on some crystal faces. Positive identification was made by using the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the metamorphic rocks. The physical properties of limonite are highly variable owing to varying chemical composition and habit; but at this location, it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and very fragile.

Malachite - Cu2(CO3)(OH)2 (Hydrous Copper Carbonate)

Malachite commonly occurs as a green film on the copper-containing metamorphic rocks. It is found mostly in granular masses, but some radiating crystal aggregates are present. Malachite is semi-hard (3.5 - 4.0), displays good cleavage, has a vitreous to silky luster, a light green streak, and is varying hues of green in color. It is commonly associated with azurite.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as microcrystalline masses in the fractures and contacts, as a result of hydrothermal activity. It is also abundant throughout the tailings piles. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage, but conchoidal fractures are evident, and has a vitreous luster.

GENESEE

Little Potlatch Creek

Legal Description: Ownership:

SW1/4, SE1/4, SE1/4, Don Dennler

Sec. 35, T38N, R4W Juliaetta ID 83535

Latah County, Idaho Phone: (208) 276-7421

Green Knob Quadrangle, Idaho

7.5 Minute Series (Topographic)

Latah County Map Series

The Little Potlatch Creek location is approximately 7.5 miles east-northeast of Genesee (Figure 6). The medium to fine grained metamorphic syenite in the roadcuts is primarily white in color with varying degrees of yellowish-brown iron staining. The bed of the intermittent stream at this location is interesting mineralogically with the main mineral of interest being corundum. A short walk to the east down to Little Potlatch Creek will provide the opportunity to see garnet in the garnet-biotite gneiss metamorphic rocks. Other outcrops in the immediate area contain metamorphosed diorite.

Road Log: (refer to Figure 6)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed south on U.S. 95 towards Genesee.

14.1 Turn left at junction of U.S. 95 and Genesee Road; proceed east

through Genesee on Genesee-Juliaetta Road.

22.3 Stop! Cabled farm access road is to the right (east). With

permission, proceed along the farm road.

23.1 Stop! Boulders of metamorphosed syenite are on both sides of

the road. The intermittent creek bed is to the left.

A short walk downhill to the east are the garnet-biotite gneiss

rocks along Little Potlatch Creek.

Figure 6: Map to syenite location east of Genesee, Idaho.

This location is more suitable for university level mineralogy or petrology classes, as the access may include considerable hiking. A certain amount of digging may also be neccessary. The Latah County map code is 5.

Minerals Present:

Apatite Muscovite

Biotite Phlogopite

Corundum Pyrite

Garnet Zircon

Microcline

Mineral Appearances:

Apatite - Ca5(PO4)3(F,Cl, OH) (Calcium Phosphate)

Apatite ocurrs as hexagonal prismatic crystals in alkaline feldspar granite. The crystals are stubby, and commonly terminated by pyramidal faces, and range in size from 1 mm to 3 mm long. Apatite has a hardness of 5.0, with a vitreous luster, a white streak, and is greenish-white in color. X-ray diffraction in the laboratory provided positive identification of this mineral.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphosed diorite and gneiss, and as disseminated plates in the granite. The crystals range in size from <1 mm to 3 mm across. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish-black color.

Corundum - Al2O3 (Aluminum Oxide)

The corundum occurs as small hexagonal crystals ranging in size from 1 mm to 5 mm. They are most abundant in the bed of the intermittent creek. However, it may be neccessary to dig down two or three feet and sieve the gravel to find them. Corundum is very hard (9.0) with an adamantine or dull vitreous luster and is gray-black to grayish-white in color.

Garnet (almandine/pyrope) - (Fe,Mg)3Al2(SiO4)3

(Iron Magnesium Aluminum Silicate)

Almandine/pyrope garnets are found at this location. The samples are in the garnet-biotite gneiss and display distinct dodecahedral crystal form, have a hardness of 6.5 - 7.5, and are bright red in color. The crystals are relatively small, ranging in size from 1 - 3 mm. Positive identification was obtained by use of X-ray diffraction in the laboratory.

Microcline - KAlSi3O8 (Potassium Aluminum Silicate)

Microcline occurs as small prismatic crystals, ranging in size from 0.5 mm to 5 mm, and as granular aggregates in the syenite. Microcline is hard (6.0 - 6.5), has nearly right angle cleavage, a vitreous luster, a white streak, and is pinkish-white in color. Identification was verified by the use of the X-ray diffractometer in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite mica occurs as small (~ 5 mm) thin disseminated plates in the diorite. These flexible, elastic plates exhibit perfect basal cleavage, prominent vitreous luster, and a silvery or yellowish-white color.

Phlogopite - K(Mg,Fe)3(AlSi3)O10(F,OH)2

(Hydrous Potassium Aluminum Silicate)

Phlogopite mica occurs as very small (~ 1 mm) six-sided plates in the metamorphosed syenite. It displays perfect basal cleavage with vitreous or pearly luster, and is yellowish-brown in color.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes, ranging in size from 0.1 mm to 0.2 mm and as compact granular aggregates in the syenite. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow than chalcopyrite.

Zircon - ZrSi04 (Zirconium Silicate)

Zircon crystals ranging in size from 0.5 mm to 4.0 mm are present in the metamorphosed syenite. The crystals are generally dipyramidal and yellowish-brown in color. Zircon is very hard (7.5) with conchoidal fractures and an adamantine to vitreous luster. Positive identification of this mineral was made by using the X-ray diffractometer in the laboratory.

GOLD BUG PROSPECT

Legal Description: Ownership:

SE1/4, SW1/4, Sec 20, T42N, R3W U.S. Government

Latah County, Idaho Potlatch Ranger Station

Harvard Quadrangle, Idaho Potlatch ID 83855

7.5 Minute Series (Topographic) Phone: (208) 875-1131

Latah County Map Series

The Gold Bug prospect is located north of Harvard, Idaho (Figure 7). The prospect is approximately 3.5 miles up Jerome Creek Road, in a northwesterly direction off of State Highway 6, at the head of Heath Gulch. It is approximately 1/4 mile north of the Gold Hill prospect on the other side of the ridge. Igneous rocks occur at this location with considerable hydrothermal alteration and metamorphic quartzite. There is one adit and a 300 ft. vertical shaft. The tailings piles contain a wide variety of minerals.

Road Log: (refer to Figure 7)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch,

Princeton, and Harvard.

29.9 Turn left on Old River Road.

30.3 Turn left on Jerome Creek Road.

33.2 Y. Take right fork (FSR #788) and continue on Jerome Creek Road.

33.5 Y. Take left fork.

33.7 Stop! Walk straight up the ridge to the left (south) to an old road. The climb is fairly steep and covers about 300 yards. The road is overgrown with small trees, but it is not brushy and hard to navigate. Turn to the right (west) and follow the old road approximately 1/4 mile to the prospect site.

Figure 7: Map to Gold Bug prospect north of Harvard, Idaho.

This location is most suitable for students in junior high or high school, as well as university-level mineralogy and petrology students. The hike to the prospect is probably a little extreme for younger students. It is an excellent location geologically, and the mineral specimens are plentiful. The Latah County map code is 6.

Minerals Present:

Ankerite Hematite

Arsenopyrite Limonite

Augite Microcline/Albite (Perthite)

Biotite Pyrite

Chalcopyrite Pyrolusite

Goethite Quartz

Mineral Appearances:

Ankerite - CaFe(CO3)2 (Calcium Iron Carbonate)

Ankerite occurs as semi-rhombohedral crystals with slightly curved faces, and as compact, fine-grained aggregates. It has a hardness of 3.5 - 4.0 and a vitreous to pearly luster. Ankerite is generally a yellowish- white color, but oxidation may cause it to be a yellowish-brown. This mineral is very similar to dolomite, both physically and chemically, except for the color. Positive identification was made with the use of the X-ray diffractometer in the laboratory.

Arsenopyrite - FeAsS (Iron Arsenic Sulfide)

Arsenopyrite is present mainly as granular aggregates, but some elongated prismatic crystals with striated faces can be found. It is hard (5.5 - 6.0), has a high specific gravity, metallic luster, a black streak, and is silvery-gray in color. Identification was verified using the X-ray diffractometer in the laboratory.

Augite - (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6

(Calcium Magnesium Iron Aluminum Silicate)

Augite is present as stubby, prismatic crystals, as well as granular aggregates in the gabbro. The physical properties vary from sample to sample because augite is an intermediate member of a solid solution series between Ca-rich diopside and Fe-rich hedenbergite end members. It is hard (5.0 - 6.0) with two distinct cleavage directions at approximately 90deg. and a splintery type fracture. Augite can also be identified by its vitreous to resinous luster, greenish-gray streak, and greenish-black color.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 3 mm across and are found in the rocks in the hydrothermal veins. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish- black color.

Chalcopyrite - CuFeS2 (Copper Iron Sulfide)

Chalcopyrite occurs as compact granular masses as a result of hydrothermal activity. It has a hardness of 3.5 - 4.0, a high specific gravity, no cleavage, a greenish-black streak, and a semi-metallic luster. Chalcopyrite is dark, brassy-yellow, and is coated with an iridescent film.

Goethite - [[alpha]]-FeOOH (Iron Hydroxide)

Goethite is present in the form of amorphous, earthy masses. It is probably formed from the oxidation of iron-bearing minerals. At this location, it is very fragile, with a yellow-brown streak, an earthy luster, and is brown in color. Identification was verified using the X-ray diffractometer in the laboratory.

Hematite - Fe2O3 (Iron Oxide)

The hematite occurs as compact, earthy masses and as micaceous rhombohedral crystals. The massive form has a hardness of around 5.0, a relatively high specific gravity, an earthy luster, reddish color, and a red-brown streak. Hematite that occurs in the micaceous form has individual rhombohedral crystals. The micaceous hematite is present in two distinct arrangements. One type is referred to as lamellar (as pages in a book), and the second type is an arrangement that resembles flower petals. Both types display a shiny purplish-red iridescence and distinguishable lines similar to striations on the crystal faces. This form of hematite is softer (3.5 - 4.5) than the massive form and is gray to gray-black in color; however, the red-brown streak is the same. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the quartzite and filling the pyrite casts. The physical properties of limonite are highly variable owing to varying chemical composition and habit; but at this location, it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and is very fragile.

Microcline/Albite - (Perthite) (K,Na)AlSi3O8

(Potassium Sodium Aluminum Silicate)

This sample is not an individual mineral. It occurs as a product of exsolution with a potassium-feldspar-rich host mineral and sodium plagioclase lamella (layers). It is hard (6.0), shows distinct, nearly right angle cleavage, has a vitreous luster, a white streak, and is blue-gray in color. The crystals are stubby and prismatic with penetration twins rarely visible with a hand lens. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite.

Pyrolusite - MnO2 (Manganese Oxide)

Pyrolusite occurs as dendritic, black aggregates resembling small plant fossils (pseudo-fossils) in the fractures of the igneous and metamorphic rocks. The dendritic form is common, but some small samples (~ 1 cm across) in the form of black, earthy masses can also be found. Pyrolusite is hard (6.0 - 6.5) with a relatively high specific gravity, sub-metallic luster, and a blue-black streak.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, microcrystalline masses in the igneous rocks, and as very small hexagonal crystals in the fractures and voids as a result of hydrothermal activity. It is also abundant throughout the tailings piles. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and has a vitreous luster.

GOLD HILL LOOP

Legal Description:

The Gold Hill Loop covers most of the central and

northwestern portions of section 20, as well as the

SW 1/4 of Sec 17, SE 1/4 of Sec 18, and NE 1/4 of Sec

19, T42N, R3W.

Latah County, Idaho

Princeton and Harvard Quadrangles, Idaho

7.5 Minute Series (Topographic)

Latah County Map Series

Ownership:

Sections 18, 19, and 20 are owned by the U.S. Government

Section 17: Potlatch Corportion

Box 1016

Lewiston ID 83501

Phone: (208) 799-0123

The Gold Hill "Loop" area is located north of Harvard, Idaho (Figure 8). The loop is approximately 3.5 miles up Jerome Creek Road, in a northwesterly direction off of State Highway 6, and covers an approximate distance of 7.5 miles. Gold Hill is a topographic formation underlain by syenite intrusions into quartzite and siltite of the Belt Supergroup rocks.

Road Log: (refer to Figure 8)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch,

Princeton, and Harvard.

29.9 Turn left on Old River Road.

30.3 Turn left on Jerome Creek Road (Forest Service Road #788).

33.5 FSR #788 forms a "Y" with FSR #4706; stay to the right on #788.

33.7 There is another "Y"; again stay to the right on #788; shortly there is another "Y"; this time, bear left.

35.5 Stop #1. Quartz vein.

Massive Quartz Goethite after Pyrite

Micaceous Hematite Actinolite

Small Garnets

35.6 Stop #2. Mafic Metamorphic Rocks

Actinolite Biotite

36.1 Stop #3. Syenite

Microcline Hornblende

Apatite Epidote

37.2 Stop #4. Metamorphic Rock (quartzite)

Actinolite Epidote

39.0 Stop #5. Quartz Outcrop.

Quartz Limonite

Actinolite Malachite

39.2 Stop #6. Junction with FSR #788H

Ultramafic Metamorphic Rocks

Augite Titanite

40.1 There is a "T" in the road, bear to the left.

41.3 This is the end of the loop; continue straight to

return to State Highway 6.

Figure 8: Map to Gold Hill Loop north of Harvard, Idaho.

This location would be a suitable field trip for students at the junior high or high school level, as well as university-level mineralogy and petrology classes. It is a trip one would want to plan in the fall or late spring because of weather and road conditions. The road is maintained, but the snow is not plowed during the winter. The extremely coarse-grained syenite consists of feldspar crystals from 2 cm wide to 10 cm long. There is a variety of both igneous and metamorphic rocks, as well as visible contacts between them. The Latah County map code is 7.

Minerals Present:

Actinolite Hornblende

Apatite Limonite

Augite Malachite

Biotite Microcline

Epidote Pyrite

Goethite Quartz

Hematite Titanite (sphene)

Mineral Appearances:

Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2

(Hydrous Calcium Magnesium Iron Silicate)

Actinolite occurs as elongated prismatic crystals in both the metamorphic and igneous rocks. The color ranges from a light to dark green, and the crystals exhibit perfect cleavage parallel to the elongation direction. Actinolite is hard (5.0 - 6.0) with a vitreous to silky luster. Actinolite also occurs in a fibrous form with the same physical properties. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Apatite - Ca5(PO4)3(F,Cl,OH) (Calcium Phosphate)

Apatite occurs as hexagonal prismatic crystals in hydrothermal veins. The crystals are stubby, commonly terminated by pyramidal faces, and range in size from 1 mm to 3 mm long. Apatite has a hardness of 5.0, with a vitreous luster, a white streak, and is greenish-white in color. X-ray diffraction in the laboratory provided positive identification of this mineral.

Augite - (Ca,Na)(Mg,Fe,Al,Ti,)(Si,Al)2O6

(Calcium Magnesium Iron Aluminum Silicate)

The augite at this location most commonly occurs as granular greenish-black or greenish-brown aggregates, although short, stubby, nearly square crystals are not uncommon. The visible crystals range in size from 1 mm to 5 mm across. Augite is relatively hard (5.0 - 6.0) with two cleavage directions at approximately 90deg. and splinter type fractures. Augite exhibits a dull vitreous luster, has a gray-green streak, and is generally some shade of green in color. X-ray diffraction in the laboratory provided positive identification of this mineral.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 3 mm across and are found in the rocks in the hydrothermal veins. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish- black color.

Epidote - Ca2(Al,Fe)3Si3O12(OH)

(Hydrous Calcium Aluminum Iron Silicate)

Epidote is present in several forms in the contact metamorphic rocks. The most common forms are fibrous and granular masses, but small prismatic, greenish crystals with striated faces can be found. Epidote is hard (6.0 - 7.0) with distinct cleavage parallel to elongation direction of the crystals. It is generally various shades of green and has a vitreous luster.

Goethite - [[alpha]]-FeOOH (Iron Hydroxide)

The goethite at Stop #1 is present as a pseudomorph after pyrite. The external characteristics of the pyrite crystals have been retained, but the pyrite has altered to goethite. Goethite has a hardness of 5.0 - 5.5, an earthy luster, a greasy feel, and is a brownish-yellow color.

Hematite - Fe2O3 (Iron Oxide)

The hematite occurs as compact, earthy masses and as micaceous rhombohedral crystals. The massive form has a hardness of around 5.0, a relatively high specific gravity, an earthy luster, reddish color, and a red-brown streak. Hematite that occurs in the micaceous form has individual rhombohedral crystals. The micaceous hematite is present in two distinct arrangements. One type is referred to as lamellar (as pages in a book), and the second type is an arrangement that resembles flower petals. Both types display a shiny purplish-red iridescence and distinguishable lines similar to striations on the crystal faces. This form of hematite is softer (3.5 - 4.5) than the massive form and is gray to gray-black in color; however, the red-brown streak is the same. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Hornblende - (Ca,Na)2-3(Mg,Fe2+,Fe3+,Al)5(Al,Si)8O22(OH)2

(Complex double chain silicate; amphibole)

Hornblende is present, along with the actinolite, in the syenite, in the form of short, stubby, black, prismatic crystals. They are hard (5.0 - 6.0) with uneven fractures, good prismatic cleavage, a vitreous luster, and a yellow-white streak. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the quartzite and filling the pyrite casts. The physical properties of limonite are highly variable owing to varying chemical composition and habit; but at this location, it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and is very fragile.

Malachite - Cu2(CO3)(OH)2 (Hydrous Copper Carbonate)

Malachite commonly occurs as a green film on the copper-containing quartz veins. It is found mostly in granular masses, but some radiating crystal aggregates are present. Malachite is semi-hard (3.5 - 4.0), displays good cleavage, has a vitreous to silky luster, a light green streak, and is varying hues of green in color. It is commonly associated with azurite, but azurite was not found.

Microcline/Albite - (Perthite) (K,Na)AlSi3O8

(Potassium Sodium Aluminum Silicate)

This sample is not an individual mineral. It occurs as a product of exsolution with a potassium-feldspar-rich host mineral and sodium plagioclase lamella (layers). It is hard (6.0), shows distinct, nearly right angle cleavage, has a vitreous luster, a white streak, and is white in color. The crystals are large, ranging in size from approximately 2 cm wide to as much as 5 cm long, up to very large (2 cm wide and 10 cm long) crystals in the syenite. Positive identification was attained by the use of the X-ray diffractometer, and the Scanning Electron Microscope in the laboratory.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates, mainly in the quartz in the hydrothermal veins. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, compact, concretionary masses in the igneous rocks, and as very small hexagonal crystals in the fractures and voids as a result of hydrothermal activity. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are milky-quartz. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and has a vitreous luster.

Titanite (Sphene) - CaTiSiO5 (Calcium Titanium Silicate)

Titanite is present in the igneous rocks and metamorphic contacts as flat, stubby, wedge-shaped crystals. It is relatively hard (5.0 - 5.5), has a fairly high specific gravity, an adamantine or resinous luster, and is a honey-brown color. X-ray diffraction in the laboratory provided positive identification of this mineral.

GOLD HILL PROSPECT

Legal Description: Ownership:

NE1/4, NW1/4, Sec. 29, T42N, R3W U.S. Government

Latah County, Idaho Potlatch Ranger Station

Harvard Quadrangle, Idaho Potlatch ID 83855

7.5 Minute Series (Topographic) Phone: (208) 875-1131

Latah County Map Series

The Gold Hill prospect is located north of Harvard, Idaho (Figure 9). The prospect is approximately three miles up Jerome Creek Road, in a northwesterly direction off of State Highway 6, at the head of Jack Gulch. There are three adits, one along the small unnamed creek, one approximately 150 ft. up the south slope, and a third 30 ft. above the second adit (Hubbard, 1957). The adits are all closed but the tailings piles contain many mineral varieties. The rocks at this location are igneous rocks with considerable hydrothermal alteration and quartzite.

Road Log: (refer to Figure 9)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch,

Princeton, and Harvard.

29.9 Turn left on Old River Road.

30.3 Turn left on Jerome Creek Road.

32.8 Turn left on Forest Service Road #4706.

33.0 Turn right on Forest Service Road #4706A.

33.3 Stop! The first adit and tailings piles are straight ahead, as

well as to the left.

Figure 9: Map to Gold Hill prospect north of Harvard, Idaho.

This location provides an excellent trip for students of all ages. The mineral specimens are plentiful, and access to the area is very easy. The Latah County map code is 8.

Minerals Present:

Albite/Microcline Microcline/Albite

(antiperthite) (perthite)

Chalcopyrite Pyrite

Ferroactinolite Quartz

Gold Sulfur

Hematite Titanite (sphene)

Mineral Appearances:

Albite/Microcline - (Antiperthite) (Na,K)AlSi3O8

(Sodium Potassium Aluminum Silicate)

This sample is not an individual mineral. It occurs as a product of exsolution with a sodium-plagioclase-rich host mineral and potassium feldspar lamella (layers). It is hard (6.0), shows distinct, nearly right angle cleavage, has a vitreous luster, a white streak and is grayish-pink in color. The crystals are bladed, with striations visible with a hand lens only on rare specimens. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Chalcopyrite - CuFeS2 (Copper Iron Sulfide)

Chalcopyrite occurs as compact granular masses as a result of hydrothermal activity. It has a hardness of 3.5 - 4.0, a high specific gravity, a greenish-black streak, and a semimetallic luster. Chalcopyrite is dark, brassy-yellow in color and is coated with an iridescent film.

Ferroactinolite - Ca2Fe5Si8O22(OH)2 (Calcium Iron Silicate)

Ferroactinolite occurs as aggregates of elongated prismatic crystals in the mafic metamorphic rocks and intrusive igneous gabbro. It has a hardness of 5.0 - 6.0, perfect 60deg./120deg. prismatic cleavage, a vitreous luster, and is greenish-black in color. It is the iron-rich end-member of the tremolite-actinolite-ferroactinolite solid-solution series.

Gold - Au (Native Element)

Gold is present, in minute amounts, as very small, shapeless grains and flakes. It is fairly soft (2.5 - 3.0) and malleable. The gold occurs in pyrite casts where the pyrite and limonite have weathered out, leaving the gold along the sides and base of the cast.

Hematite - Fe2O3 (Iron Oxide)

The hematite occurs as compact, earthy masses and as micaceous rhombohedral crystals. The massive form has a hardness of around 5.0, a relatively high specific gravity, an earthy luster, reddish color, and a red-brown streak. Hematite that occurs in the micaceous form has individual rhombohedral crystals. The micaceous hematite is present in two distinct arrangements. One type is referred to as lamellar (as pages in a book), and the second type is an arrangement that resembles flower petals. Both types display a shiny purplish-red iridescence and distinguishable lines similar to striations on the crystal faces. This form of hematite is softer (3.5 - 4.5) than the massive form and is gray to gray-black in color; however, the red-brown streak is the same. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Microcline/Albite - (Perthite) (K,Na)AlSi3O8

(Potassium Sodium Aluminum Silicate)

This sample is not an individual mineral. It occurs as a product of exsolution with a potassium-feldspar-rich host mineral and sodium plagioclase lamella (layers). It is hard (6.0), shows distinct, nearly right angle cleavage, has a vitreous luster, a white streak and is blue-gray in color. The crystals are stubby and prismatic with penetration twins visible with a hand lens on rare specimens. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, microcrystalline masses in the igneous rocks, and as very small hexagonal crystals in the fractures and voids as a result of hydrothermal activity. It is also abundant throughout the tailings piles. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and has a vitreous luster.

Sulfur - S (Native Element)

Sulfur occurs as very fine granular aggregates and encrustations, which are probably an alteration product of pyrite. It has a yellowish-brown color, very soft (1.5 - 2.5), extremely fragile with poor cleavage, and has a resinous to earthy luster. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Titanite (sphene) - CaTiSiO5 (Calcium Titanium Silicate)

Titanite is present in the igneous rocks as flat, stubby, wedge-shaped crystals. It is relatively hard (5.0 - 5.5), has a fairly high specific gravity, an adamantine or resinous luster, and is a honey-brown color. X-ray diffraction in the laboratory provided positive identification of this mineral.

HARVARD-DEARY CUTOFF

BASALT QUARRY

Legal Description: Ownership:

NE1/4, NW1/4, SE1/4, Potlatch Corporation

Sec. 9, T41N, R3W Northern Woodlands

Latah County, Idaho Bovill ID 83806

Harvard Quadrangle, Idaho Phone: (208) 826-3511

7.5 Minute Series (Topographic)

Latah County Map Series

The Harvard-Deary cutoff basalt quarry is located between Princeton and Harvard. It is approximately 1/2 mile south of the junction of Idaho State Highway 6 and Idaho State Highway 9 on the left (east) side of Highway 9 (Figure 10). The 60 to 120 ft. high outcrop belongs to the Potlatch flow, of the Onaway Member, of the Wanapum Formation, of the Columbia River Basalt Group.

Road Log: (refer to Figure 10)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch and Princeton.

25.7 Turn right of State Highway 9 towards Deary.

26.2 Turn left onto a gravel, gated driveway. Stop! The quarry is

a short walk (200 yards) up the gravel access road.

Figure 10: Map to Harvard-Deary Cutoff basalt quarry.

This location is a good place to take students of any grade level. It is easily accessible during all seasons. The Latah County map code is 9.

Minerals Present:

Aragonite Limonite

Calcite Nontronite

Hematite Olivine

Labradorite Opal

Mineral Appearances:

Aragonite - CaCO3 (Calcium Carbonate)

Aragonite occurs as small, acicular (needle-like), radiating

crystals within the vugs of the basalt. These elongated prismatic crystals are semi-hard (3.5 - 4.0) and very fragile with a vitreous luster, a white streak, and a brownish-yellow to white color.

Calcite - CaCO3 (Calcium Carbonate)

The calcite is yellowish to white and is found as a secondary coating or filling in the fractures in the basalt. Calcite is easily identified by its concretionary form, hardness (3.0), and effervescent reaction with dilute hydrochloric acid.

Hematite - Fe2O3 (Iron Oxide)

Hematite occurs as compact, granular masses. It is relatively hard (5.5 - 6.5), has a high specific gravity, exhibits no cleavage, has an earthy luster, produces a red-brown streak, and is a deep red color.

Labradorite (plagioclase) - (Ca,Na)AlSi3O8

(Calcium, Sodium Aluminum Silicate)

The plagioclase feldspar present at this location is a solid solution between anorthite and albite end-members and contains equal amounts of calcium and sodium. The elongated, white to yellow to yellowish- green crystals are small (~ 2 mm long and 0.5 mm across), and display a slight play on colors giving off an iridescent blue color. Plagioclase has a hardness of 6.0, a vitreous to pearly luster, nearly perfect 90deg. cleavage, and striations on some crystal faces. Positive identification was made by using the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the basalt. The physical properties of limonite are highly variable owing to varying chemical composition and habit, but at this location it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and is very fragile.

Nontronite - Na0.3Fe2(Al,Si)4O10(OH)2(H2O)4 (Clay Mineral)

Nontronite is a secondary mineral formed by the weathering of the aluminum silicates in the basalt. It occurs as microcrystalline masses filling the vugs in the basalt. It is extremely soft (1.5 - 2.0) and commonly has a dull or earthy luster, except on very fresh surfaces, where a vitreous luster is displayed. As soon as the samples are exposed to the atmosphere, the luster quality decreases and the color changes from a pale blue to a dull greenish blue. The identification of this mineral was verified using the X-ray diffractometer in the laboratory.

Olivine - (Mg,Fe)2SiO4 (Magnesium Iron Silicate)

The olivine at this location occurs mainly as very small crystals in the basalt. However, it can also be found as small, stubby, prismatic crystals that are visible with the naked eye or with a hand lens. Olivine has a hardness of 6.5 - 7.0, conchoidal fractures, a vitreous luster, and is yellow-green or olive-green in color.

Opal - SiO2*nH2O (Hydrous Silicon Oxide)

The white or clear opal is found in a massive microcrystalline form filling the vugs in the basalt. The differences in color of the opal samples may be due to varying impurities in the specimens. Opal is relatively easy to identify. It has a hardness of 5.5 - 6.5, low specific gravity, and a vitreous or greasy luster. It is also fragile with very small conchoidal fractures present in nearly all of the samples.

HARVARD PARK

Legal Description: Ownership:

SE1/4, NW1/4, NW1/4, Latah County

Sec. 9, T41N, R3W 5th and Van Buren

Latah County, Idaho Moscow ID 83843

Harvard Quadrangle, Idaho Phone: (208) 882-8580

7.5 Minute Series (Topographic)

Latah County Map Series

This outcrop is located directly north of State Higway 6 west of the park in Harvard (Figure 11). The metamorphic rock types have been mapped as belonging to the Libby Formation of the Belt Supergroup.

Road Log: (refer to Figure 11)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch and Princeton and continue on to Harvard.

26.0 Turn left into small gravel parking area at the west side of

the park in Harvard. Stop! The outcrop is straight ahead in the side of the ridge.

Figure 11: Map to metamorphic outcrop in Harvard, Idaho.

This location is a good place to take students of any grade level. It is easily accessible during all seasons. It is also an opportunity to collect minerals that occur in metamorphic rocks. The Latah County map code is 10.

Minerals Present:

Actinolite

Calcite

Epidote

Quartz

Scapolite

Mineral Appearances:

Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2

(Hydrous Calcium Magnesium Iron Silicate)

Actinolite occurs as striated, elongated prismatic crystals in both the metamorphic and igneous rocks. The color ranges from a light to dark green, and the crystals exhibit perfect cleavage parallel to the elongation direction. Actinolite is hard (5.0 - 6.0) with a vitreous to silky luster. Actinolite also occurs in a fibrous form with the same physical properties. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Calcite - CaCO3 (Calcium Carbonate)

The calcite is yellowish to white and is found as a secondary coating or filling in the fractures in the metamorphic rocks. Calcite is easily identified by its concretionary form, hardness (3.0), and effervescent reaction with dilute hydrochloric acid.

Epidote - Ca2(Al,Fe)3Si3O12(OH)

(Hydrous Calcium Aluminum Iron Silicate)

Epidote is present in several forms in the contact metamorphic rocks. The most common forms are fibrous and granular masses, but small prismatic, greenish crystals with striated faces can be found. Epidote is hard (6.0 - 7.0) with distinct cleavage parallel to elongation direction of the crystals. It is generally various shades of green and has a vitreous luster.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, microcrystalline masses in the fractures and voids as a result of hydrothermal activity. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, wheras freshly broken samples are milky-quartz. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and it has a vitreous luster.

Scapolite - (Na,Ca,K)4Al3(Al,Si)3Si16O24(Cl,SO4,CO3)

(Complex Silicate)

Scapolite occurs as microgranular masses or aggregates in and on the metamorphic rocks at this site. Some very small prismatic crystals can be seen with the aid of a hand lens. Scapolite has a hardness of 5.0 - 6.5, very poor cleavage, a dull vitreous luster, and is grayish-white in color. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

IDAHO HIGHWAY 3 ROADCUT

BETWEEN KENDRICK & DEARY

Legal Description: Ownership:

NE1/4, SE1/4, SE1/4, Sec18, T38N, R2W State of Idaho

Latah County, Idaho Department of Roads

Cedar Ridge Quadrangle, Idaho Phone: (208) 882-5125

7.5 Minute Series (Topographic) (Moscow Office)

Latah County Map Series

The roadcut is located approximately three miles northeast of Kendrick, Idaho along State Highway 3 between Kendrick and Deary (Figure 12). It is easily found, as you travel up the grade northeast out of Kendrick it is the first roadcut where there are steep Columbia River Basalt outcrops on both sides of the highway.

Road Log: (refer to Figure 12)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 through Troy.

11.7 From the east side of Troy, turn right on State Highway 99.

22.9 In Kendrick, turn left on State Highway 3.

25.9 Stop! Large outcrop on left side of highway.

Small outcrop on right side of highway.

The best mineral samples are on the ledge approximately 25 feet above ground level on the left side of the highway. This location would be best suited for students from the fifth grade or older because some light climbing is required to reach the ledge. The Latah County map code is 11.

Figure 12: Map to Roadcut northeast of Kendrick, Idaho.

Minerals Present:

Pyrolusite

Red Opal

White Opal

Wood Opal

Mineral Appearances:

Pyrolusite - MnO2 (Manganese Oxide)

Pyrolusite occurs as dendritic, black aggregates resembling small plant fossils (pseudo-fossils). The dendritic form is the most common type, but some small samples (~ 1 mm across) in the form of black, earthy masses can also be found. Pyrolusite is hard (6.0 - 6.5) with a relatively high specific gravity, sub metallic luster, and a blue-black streak.

Red Opal - SiO2*nH2O (Hydrous Silicon Oxide)

The red opal occurs primarily as botryoidal, globular masses on the outside of the basalt. It also occurs in a fibrous, radiating, acicular form coating the basalt and filling the vugs in the basalts.

White or Clear Opal - SiO2*nH2O (Hydrous Silicon Oxide)

The white or clear opal is found as botryoidal, globular masses encrusting the basalt, as well as being present within the vugs in the basalt. The white opal also occurs in a fibrous, radiating, acicular form coating the basalt and filling the vugs in the basalts.

The differences in color of the opal samples may be due to varying impurities in the specimens. Opal is relatively easy to identify. It has a hardness of 5.5 - 6.5, low specific gravity, and a vitreous or greasy luster. It is also fragile with very small conchoidal fractures present in nearly all of the samples.

Wood Opal - SiO2*nH2O (Hydrous Silicon Oxide)

This variety of opal is formed by silica replacement of fibers in fossilized wood. The original texture and detail of the wood material is preserved in mineral form. It is present as microcrystalline masses ranging in size from 2 to 6 cm in diameter.

MICA MOUNTAIN

MUSCOVITE MINE

Legal Description: Ownership:

SW1/4, SW1/4, NE1/4, Sec 22, T41N, R2W Alice Brady and

Latah County, Idaho Eleonor Felton

Mica Mountain Quadrangle, Idaho 707 East E Street

7.5 Minute Series (Topographic) Moscow ID 83843

Latah County Map Series Phone: (208) 882-2978

The Mica Mountain muscovite mine is located approximately 10 miles north-northwest of Deary, Idaho (Figure 13). Muscovite-biotite schists and gneisses representing Belt Supergroup metamorphic rocks underlay most of the area (Hubbard, 1957). Granitic pegmatite, ranging in size from 10 to 100 meters, is contained within the metamorphic rocks and was formed by hydrothermal replacement of the Belt rocks (Anderson, 1933).

Road Log: (refer to Figure 13)

0.0 From junction of US 95 and State 8 in Moscow; proceed east on State 8 through Troy and on towards Deary, Idaho.

11.6 From the east side of Troy, continue following Highway 8 towards Deary.

24.1 Turn left on State Highway 9.

26.5 Turn right on Mica Mountain Road.

0.0 Proceed north across the wooden bridge.

1.5 Forest Service Road #3347 bears right toward Vassar Meadows

but keep going straight.

1.7 There is a "Y" in the road. Turn right on FSR #3848 (also called Mica Mountain Road).

7.5 Another "Y" with the left leading to the old load-out site.

Stay to the right to get to the mine pit and tailings piles.

7.6 Stop. A short walk (less than 1/4 mile) up the trail to the left will lead to the pit.

The Mica Mountain muscovite mine is an excellent location to take students of all ages. The metamorphic schist and granite pegmatite are very indicative of the geologic processes that take place in the earth. A wide variety of minerals are also present. The Latah County map code is 12.

Figure 13: Map to Mica Mountain muscovite mine

north of Deary, Idaho.

Minerals Present:

Albite Muscovite

Beryl Phlogopite

Biotite Quartz

Garnet Tourmaline

Mineral Appearances:

Albite (plagioclase feldspar) - NaAlSi3O8

(Sodium Aluminum Silicate)

Albite is present as small bladed crystals or weathered granular masses in the pegmatite. Owing to its size, habit, and similarity to other feldspar minerals, positive identification is very difficult in hand sample. The use of the X-ray diffractometer and observation of the optical properties provided definite identification.

Beryl - Be3Al2Si6O18 (Beryllium Aluminum Silicate)

Beryl occurs in the pegmatites as hexagonal prisms without terminations. The color varies from yellowish-white to pale-green. The hexagonal crystals vary in size from 1 cm across and 2 to 3 cm in length to as large as 8 cm across and 15 cm long. It is very hard (7.5 - 8.0) with a vitreous luster and a white streak. The samples contain inclusions of quartz, and are weathered, fractured, and fragile.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks. The crystals range in size from <1 mm to 5 cm and are the primary constituent of the mica schist in this area. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish-black color.

Garnet - (almandine-pyrope) - (Fe,Mg)3Al2(SiO4)3

(Iron Magnesium Aluminum Silicate)

The garnets found at this location are almandine/pyrope. The samples are in the pegmatite and display distinct dodecahedral crystal form, have a hardness of 6.5 - 7.5, and are bright red in color. The crystals are relatively small, ranging in size from 1 to 3 mm. Positive identification was obtained through the use of X-ray diffraction in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite occurs as foliated, tabular, pseudo-hexagonal crystals in the granite pegmatite and at the contact between the pegmatite and the metamorphic rocks. Some of the sheets are as large as 20 to 30 cm across, although smaller crystals in the 1 to 5 cm range are more common. The muscovite has perfect basal cleavage into thin, flexible, elastic sheets. It is soft (2 - 2.5) and is primarily yellow-brown in color where occurring in thick, foliated books, but clear colored where present in thin sheets.

Phlogopite - K(Mg,Fe)3(AlSi3)O10(F,OH)2

(Hydrous Potassium Aluminum Silicate)

Phlogopite occurs as very small (~ 1 to 2 mm) plates in the metamorphic rocks. It can be identified by its basal cleavage, vitreous luster, and yellowish-brown color.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as microcrystalline masses in the pegmatite, as well as being abundant throughout the tailings piles. The quartz that has been exposed is coated with a yellow or red-brown iron stain, whereas the quartz in the pegmatite is more of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and has a vitreous luster.

Tourmaline (schorl) -

(Na,Ca) (Mg, Fe2+,Fe3+,Al,Mn,Li)3Al6(B03)3(Si6O18)(OH,F)4

(Complex Borosilicate)

The schorl variety of tourmaline is rich in iron and sodium. It occurs as elongated, black prismatic crystals with vertical striations in the mica schist, and short, stubby, black crystals in the pegmatite. The elongated crystals are commonly 1 to 4 mm across and 1 to 2 cm long. Tourmaline is very hard (7.0) with conchoidal fractures and a vitreous luster. The luster changes to resinous on the fractured surfaces.

MIZPAH MINE

Legal Description: Ownership:

NE1/4, SW1/4, Sec 8, T42N, R2W U.S. Government

Latah County, Idaho Potlatch Ranger Station

Abes Knob Quadrangle, Idaho Potlatch ID 83855

7.5 Minute Series (Topographic) Phone: (208) 875-1131

Latah County Map Series

The Mizpah mine is located approximately 17.5 miles northeast of Harvard, Idaho via the Palouse River Road and Fosest Service Road #447 (Figure 14). Metamorphic rocks (schist and quartzite), along with hydrothermal alteration veins occur at this location. There is a mine shaft and several adits into the hill sides, but mineral specimens are plentiful in the tailings piles.

Road Log: (refer to Figure 14)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on U.S. 95 towards Potlatch.

16.3 Turn right on State Highway 6; proceed east through Potlatch, Princeton, and Harvard.

30.5 Turn right on Palouse River Road (to Laird Park & Camp Grizzly).

0.0 From junction of State 6 and Palouse River Road.

1.5 Pavement ends but well-kept gravel road continues.

1.8 Cross the bridge, and turn left on Forest Service Road #447

6.7 Turn right on FSR #447, and cross the North Fork of the

Palouse River.

11.0 Turn left on FSR #1432.

11.1 Turn left on Mizpah Creek Road Trail #345.

11.9 There is a "Y" in the road; bear to the right.

12.1 The road turns to the right; take the four-wheel-drive trail

straight ahead.

13.0 Stop and walk on up the trail approximately 0.5 mile.

There will be a mine shaft and tailings piles directly

along side of the trail.

Figure 14: Map to Mizpah mine northeast of Harvard, Idaho.

This location would provide a suitable field trip for students of any grade level, but would probably be more interesting to junior high and high school students. University mineralogy classes would find this site very rewarding with its wide variety of minerals. The Latah County map code is 13.

Minerals Present:

Arsenopyrite Cuprite Pyrrhotite

Azurite Copper Quartz

Bornite Hematite Staurolite

Brochantite Limonite Tourmaline

Chalcocite Malachite Zinnwaldite (?)

Chalcopyrite Pyrite

Mineral Appearances:

Arsenopyrite - FeAsS (Iron Arsenic Sulfide)

Arsenopyrite occurs as slightly elongated prismatic crystals ranging in size from 1 mm to as large as 1 cm, and granular aggregates in the hydrothermal vein and metamorphic rocks. It is relatively hard (5.5 - 6.0) with a metallic luster and a black streak.

Azurite - Cu3(CO3)2(OH)2 (Hydrous Copper Carbonate)

Azurite occurs as very small, striated, tabular, prismatic, radiating, intergrown crystals in the rocks found in the hydrothermal veins, and as a granular film coating the copper-bearing metamorphic rocks. This secondary copper mineral is semi-hard (3.5 - 4.0), displays good cleavage with a vitreous luster and a pale blue streak. It is commonly associated with malachite. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

Bornite - Cu5FeS4 (Copper Iron Sulfide)

Bornite can be found as octahedral crystals at this location, but it is more likely to be found as compact granular masses. It commonly displays a reddish-bronze color, which is tarnished to an iridescent purple and blue film. The old miners referred to bornite as "Peacock Ore." Bornite has a hardness of 3.0, a high specific gravity, a gray-black streak, and a metallic luster.

Brochantite - Cu4(SO4)(OH)6 (Hydrous Copper Sulfate)

Brochantite is present in granular form in veins in the adit, although some small prismatic crystals (~2 mm) can be found. It is light blue-green in color with a vitreous to pearly luster and a light green streak. The brochantite is very weathered, fragile, and difficult to identify in hand sample owing to its physical similarity to other copper sulfate and copper carbonate minerals. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Chalcocite - Cu2S (Copper Sulfide)

Chalcocite exists primarily in the form of granular aggregates in the hydrothermal sulfide deposit. It is soft (2.5) with a metallic luster, a dark gray streak, and conchoidal fractures. It commonly is associated with cuprite, malachite, and azurite. Tabular crystals with striated faces can be found, but they are uncommon.

Chalcopyrite - CuFeS2 (Copper Iron Sulfide)

Chalcopyrite occurs as compact granular masses as a result of hydrothermal activity and metamorphism. It has a hardness of 3.5 - 4.0, a high specific gravity, lacks cleavage, a greenish-black streak, and a semi-metallic luster. Chalcopyrite is dark, brassy yellow in color and is coated with an iridescent film. X-ray diffraction in the laboratory provided positive identification of this mineral.

Cuprite - Cu2O (Copper Oxide)

Cuprite is present in the form of very small (< 1 mm) elongated cubic/dodecaheral crystals. It has a hardness of approximately 4.0 with a dull adamantine luster and a bright red streak. Cuprite is a dark red color and is altered to malachite on exposed surfaces. X-ray diffraction in the laboratory provided positive identification of this mineral.

Copper - Cu (Native Element)

Small amounts of copper can be found as compact, filiform masses. It displays the characteristic copper-red color on fresh surfaces. However, most samples are coated with a greenish malachite film or a blackish or iridescent film. Copper is soft (2.5 - 3.0), very heavy, and malleable with a metallic luster.

Hematite - Fe2O3 (Iron Oxide)

Hematite occurs as compact, granular masses. It is relatively hard (5.5 - 6.5), has a high specific gravity, exhibits no cleavage, has an earthy luster, produces a red-brown streak, and is a deep red color.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the metamorphic rocks. The physical properties of limonite are highly variable owing to varying chemical composition and habit, but at this location, it is yellowish-brown in color with an earthy luster, pale brown to yellow streak, and is very fragile.

Malachite - Cu2(CO3)(OH)2 (Hydrous Copper Carbonate)

Malachite commonly occurs as a green film on the copper-containing metamorphic rocks. It is found mostly in granular masses, but some radiating crystal aggregates are present. Malachite is semi-hard (3.5 - 4.0), displays good cleavage, has a vitreous to silky luster, a light green streak, and is varying hues of green. It is commonly associated with azurite. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite. X-ray diffraction in the laboratory provided positive identification of this mineral.

Pyrrhotite - Fe1-xS (Iron Sulfide)

Pyrrhotite occurs mainly as massive, granular aggregates in the hydrothermal vein and the metamorphic rocks surrounding the mine. Very small tabular crystals are less common. It has a hardness of around 4.0, a metallic luster, is slightly magnetic, and is bronzish- black in color.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as microcrystalline masses in the fractures and contacts as a result of hydrothermal activity. It is also abundant throughout the tailings piles. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage, but conchoidal fractures are evident, and has a vitreous luster.

Staurolite - (Fe,Mg,Zn)2Al9Si4O23(OH)

(Hydrous Iron Magnesium Aluminum Silicate)

Staurolite occurs as prismatic crystals, up to 4 cm long, in the schist surrounding the mine site. The surface of the mineral is covered with a dull earthy coating resulting from alteration processes. Removing the coating reveals crystals that are brownish- black in color, display a resinous or vitreous luster, and have a hardness of about 7.0. Single crystal occurrences are the most common, but samples exhibiting cruciform twinning can be found.

Tourmaline (schorl) -

(Na,Ca) (Mg, Fe2+,Fe3+,Al,Mn,Li)3Al6(B03)3(Si6O18)(OH,F)4

(Complex Borosilicate)

The schorl variety of tourmaline is rich in iron and sodium. It occurs as elongated, black prismatic crystals with vertical striations in the mica schist. The elongated crystals are commonly 1 to 4 mm across and 0.5 to 1 cm long, and are in the form of radiating or parallel aggregates. Tourmaline is very hard (7.0) with conchoidal fractures and a vitreous luster. The luster changes to resinous on the fractured surfaces.

Zinnwaldite (?) - KLiFe3+Al(AlSi3)O10(F,OH)2

(Hydrous Potassium Aluminum Silicate)

Zinnwaldite is present as tabular or bladed crystals in the hydrothermal vein in conjunction with quartz. It is soft (2.5 - 3.0) with prominent basal cleavage, a vitreous to greasy luster, and is silvery-black in color. X-ray diffraction patterns match those for zinnwaldite, but chemical analysis is needed for positive identification.

NIRK BASALT QUARRY

NEAR POTLATCH ID

Legal Description: Ownership:

NE1/4, NE1/4, NW1/4, Sec. 31, T43N, R4W Ronald J. Nirk

Latah County, Idaho Rt. 1 Box 77

Mission Mountain Quadrangle, Idaho Potlatch ID 83855

7.5 Minute Series (Topographic) Phone: (208) 885-1372

Latah County Map Series

The Nirk basalt quarry is located approximately 7.5 miles north and 0.3 mile west of Potlatch along U.S. Highway 95 on the west side of the road (Figure 15). The 50 to 60 ft. thick outcrop belongs to the Potlatch flow, of the Onaway Member, of the Wanapum Formation, of the Columbia River Basalt Group.

Road Log: (refer to Figure 15)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed north on Highway 95.

16.3 Junction of U.S. 95 and State Highway 6; Proceed north on U.S. 95.

23.6 Turn left on gravel road, and proceed to green gate.

24.2 The quarry is approximately 100 yards straight ahead.

This location is an exciting place to stop. It is possible that a small volcano vent existed at one time. The basalt is relatively young and contains mineral crystals. The Latah County map code is 14.

Figure 15: Map to Nirk basalt quarry north of Potlatch, Idaho.

Minerals Present:

Chabazite

Labradorite

Pyrite

Mineral Appearances:

Chabazite - Ca(Al2Si4)O12*6H2O

(Hydrated Calcium Aluminum Silicate)

Chabazite occurs as rhombohedral crystals within vugs and fractures of the basalt. It is semi-hard (4 - 5), with rhombohedral cleavage, vitreous luster, and a white streak. The crystals are very large, commonly 3 to 5 mm across, with some being as large up to 1 cm in diameter and white in color with penetration twinning in all the samples. Green chabazite is also found in massive form underneath the white rhombohedral crystals. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Labradorite (plagioclase) - (Ca,Na)AlSi3O8

(Calcium, Sodium Aluminum Silicate)

The plagioclase feldspar found at this location is a solid solution between anorthite and albite end-members and contains equal amounts of calcium and sodium. The elongated, white to yellow-white to yellow-green crystals range in size from 3 mm long and 1 mm wide up to 2 cm long and 1 cm wide, and display a slight play on colors yielding an iridescent blue. Plagioclase has a hardness of 6.0, a vitreous to pearly luster, nearly perfect 90deg. cleavage, and striations on some crystal faces. Positive identification was made by using the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Pyrite - FeS2 (Iron Sulfide)

Pyrite is a secondary mineral occurring in the form of very small cubic crystals on the basalt. It can be identified by its brassy yellow color and cubic habit.

PALOUSE DIVIDE ROAD (FSR 377)

Legal Description: Ownership:

Sections 12, 11, 2, 3, & 4, U.S. Forest Service

T41N, R1W, and St. Maries Ranger District

Sections 32, 29, 21, 22, & 15 P.O. Box 407

T42N, R1W St. Maries ID 83861

Latah County, Idaho Phone: (208) 245-2531

Abes Knob Quadrangle, Idaho

7.5 Minute Series (Topographic)

Latah County Map Series

The Palouse Divide Road (Forest Service Road #377) is a stop by stop trip rather than one of specific location. The trip covers an area north-northwest of Bovill towards the Palouse Divide (Figure 16). There are several prominent outcrops of alkaline feldspar granite, granite pegmatite, mica schist, gneiss, and quartzite.

Road Log: (refer to Figure 16)

0.0 Starting point is the intersection of U.S. Highway 95 and State Highway 8 in Moscow; proceed east on Highway 8 through Troy and Deary to Bovill.

32.7 Turn left on State Highway 3 at Bovill, and proceed north through Bovill.

36.6 Turn left on Talapus Creek Road (FSR #377) towards the

Palouse Divide.

0.0 Junction of Talapus Creek Road and State Highway 3.

0.8 "Y" in the road; bear to the left.

1.7 Stop #1. Alkaline feldspar granite outcrop on the right hand side of the road.

Microcline Quartz

Titanite (sphene) Apatite (Fluorapatite)

Biotite Phlogopite

2.1 Stop #2. Another alkaline feldspar granite outcrop on the

right hand side of the road.

Same mineralogy as Stop #1.

4.0 Bear to the right on Palouse Divide Road. The road is marked

with a Forest Service sign.

4.6 FSR #377 & FSR #377B junction - continue straight ahead on FSR #377.

5.6 Stop #3. Granite pegmatite outcrop.

Microcline - crystals are 6 to 10 cm long

Quartz Biotite

Muscovite

5.7 Stop #4. FSR #377 & FSR #377C junction; stay on FSR #377.

Mica schist

Muscovite Biotite

5.9 Stop #5. Metamorphic - Igneous contact on left side of the road.

Mica schist and granite pegmatite

Same mineralogy as Stops #3 & #4

6.4 "Y" Bear to the right.

7.4 Stop #6. Quartzite outcrop

Actinolite Tremolite

Pyrolusite Limonite

7.6 Stop #7. Quartzite and gneiss

Same mineralogy as Stop #6 plus massive

smoky quartz.

10.1 Stop #8. Another metamorphic outcrop.

Same mineralogy as Stops #5 & #6 plus

hornblende.

Figure 16: Map to Palouse Divide Road (FSR #377) field trip.

This trip is definitely most suitable for university-level mineralogy and petrology classes. A basic understanding of geology is neccessary to identify some of the minerals and understand the geologic phenomena in the region. The Latah County map code is 15.

Minerals Present:

Actinolite Phlogopite

Apatite (fluorapatite) Pyrolusite

Biotite Quartz

Limonite Titanite (sphene)

Microcline Tremolite

Muscovite

Mineral Appearances:

Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2

(Hydrous Calcium Magnesium Iron Silicate)

Actinolite occurs as elongated prismatic crystals in the metamorphic rocks. The color ranges from a light to dark green, and the crystals exhibit perfect cleavage parallel to the elongation direction. Actinolite is hard (5.0 - 6.0) with a vitreous to silky luster. Actinolite also occurs in a fibrous form with the same physical properties. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Apatite (fluorapatite) - Ca5(PO4)3(F) (Phosphate)

Apatite occurs as hexagonal prismatic crystals in alkaline feldspar granite. The crystals are stubby and commonly terminated by pyramidal faces, and range in size from 1 mm to 3 mm long. Apatite has a hardness of 5.0, with a vitreous luster, a white streak, and is greenish-white in color. X-ray diffraction in the laboratory provided positive identification of this mineral.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates in the metamorphic rocks and as disseminated plates in the granite. The crystals range in size from <1 mm to 3 mm across. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish-black color.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the quartzite. The physical properties of limonite are highly variable owing to varying chemical composition and habit, but at this location, it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and very fragile.

Microcline - KAlSi3O8 (Potassium Aluminum Silicate)

Microcline occurs as small prismatic crystals and as granular aggregates in the alkaline feldspar granite and as large 6 to 10 cm long crystals in the granite pegmatite. Microcline is hard (6.0 - 6.5), has nearly right angle cleavage, a vitreous luster, a white streak, and is pinkish-white in color. Identification was verified by the use of the X-ray diffractometer in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite occurs as foliated, tabular, pseudo-hexagonal crystals in the granitic rocks. The crystals are in the 1 to 5 cm range. Muscovite has perfect basal cleavage and thin, flexible, and elastic sheets. It is soft (2 - 2.5) and is primarily yellow-brown in color in thick, foliated books, but clear where found in thin sheets.

Phlogopite - K(Mg,Fe)3(AlSi3)O10(F,OH)2

(Hydrous Potassium Aluminum Silicate)

Phlogopite mica occurs as very small (~ 1 mm) six-sided plates in the granititic rocks. It displays perfect basal cleavage with vitreous or pearly luster, and is a yellowish-brown color.

Pyrolusite - MnO2 (Manganese Oxide)

Pyrolusite occurs as dendritic, black aggregates resembling small plant fossils (pseudo-fossils). The dendritic form is the most common type, but some small samples (~ 1 mm across) in the form of black, earthy masses can also be found. Pyrolusite is hard (6.0 - 6.5) with a relatively high specific gravity, sub-metallic luster, and a blue-black streak.

Quartz - SiO2 (Silicon Oxide)

Quartz occurs as small microcrystalline grains in the alkaline feldspar granite and as large massive aggregates in the granite pegmatite.

The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage, but conchoidal fractures are evident, and has a vitreous luster.

Titanite (sphene) - CaTiSiO5 (Calcium Titanium Silicate)

Titanite is present in the alkaline feldspar granite as small, (< 1 mm) flat, stubby, wedge-shaped crystals. It is relatively hard (5.0 - 5.5), has a fairly high specific gravity, an adamantine or resinous luster, and is a honey-brown color. X-ray diffraction in the laboratory provided positive identification of this mineral.

Tremolite - Ca2Mg5Si8O22(OH)2

(Hydrous Calcium Magnesium Silicate)

Tremolite occurs as elongated prismatic crystals in the metamorphic rocks. The color ranges from a light green to white and the crystals exhibit perfect cleavage parallel to the elongation direction. Tremolite is hard (5.0 - 6.0) with a vitreous to silky luster. Tremolite also occurs in a fibrous form with the same physical properties. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

TROY-DEARY GUN CLUB

BASALT QUARRY

Legal Description: Ownership:

SE1/4, SE1/4, Sec. 25, T40N, R3W Orley E. Hunt Estate

Latah County, Idaho & Jeanetta Hunt

Stanford Quadrangle, Idaho 1020 Pleasant Hill Road

7.5 Minute Series (Topographic) Troy ID 83871

Latah County Map Series Phone: Not available

The Troy Gun Club basalt quarry is located east of Troy, Idaho (Figure 17). The quarry is approximately 1/4 mile north of State Highway 8. The 80 to 90 feet thick flow is one of the Priest Rapids flows, of the Wanapum Formation, of the Columbia River Basalt Group.

Road Log: (refer to Figure 18)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 to Troy.

11.6 From the east side of Troy, continue following Highway 8 towards Deary.

18.2 Turn left on Gun Club Road.

18.4 Turn left on the quarry access road. Follow the access road approximately 0.4 mile to the quarry.

Figure 17: Map to Troy-Deary basalt quarry east of Troy, Idaho.

This location would provide an excellent field trip for students of any grade level. The Latah County map code is the 16.

Minerals Present:

Calcite

Goethite

Opal (brown, black, & white)

Siderite

Mineral Appearances:

Calcite - CaCO3 (Calcium Carbonate)

The calcite is yellowish to white and is found as a secondary coating or filling in the fractures in the basalts. Calcite is easily identified by its concretionary form, hardness (3.0), and effervescent reaction with dilute hydrochloric acid.

Goethite - [[alpha]]-FeOOH (Iron Hydroxide)

Goethite occurs as a thin, brown, poorly crystalline coating over the botryoidal siderite. It can be distinguished from siderite by its higher degree of hardness (5.0 - 5.5) and dark brown to black color. X-ray diffraction analysis verified the identification.

Brown Opal - SiO2 * nH2O (Hydrous Silicon Oxide)

The brown opal can be found in microcrystalline masses ranging in size from granular to 4 to 6 cm in diameter.

Black Opal - SiO2 * nH2O (Hydrous Silicon Oxide)

The black opal is also found as microcrystalline masses which range in size from granular to 4 to 6 cm in diameter.

White Opal - SiO2 * nH2O (Hydrous Silicon Oxide)

The white opal occurs mainly in globular masses on the outside of the basalt.

The three varieties of 'opal' are identifiable in the field. Opal has a hardness of 5.5 - 6.5 with a relatively low specific gravity. It has a vitreous or greasy luster, and conchoidal fractures are common on nearly all samples. The differences in color of the samples may be due to varying impurities in the specimen. The three samples also have varying crystallinity based upon X-ray analysis.

Siderite - FeCO3 (Iron Carbonate)

Siderite is found as botryoidal globular masses within the vugs in the basalt. It has a hardness of 3.5 - 4.0 with a bright vitreous luster and a white streak. The color varies from a very pale brown to a pale yellow. The spheres are thinly coated with brown goethite, and range in size from 1 to 5 mm. Identification of this mineral was verified by the use of X-ray diffraction in the laboratory.

TROY SILLIMANITE PROSPECT

Legal Description: Ownership:

NE1/4, SW1/4, SW1/4, Sec.7, T39N, R2W Kenneth L. Hokanson

Latah County, Idaho 1141 Dry Creek Road

Little Bear Ridge Quadrangle, Idaho Troy ID 83843

7.5 Minute Series (Topographic) Phone: Not available

Latah County Map Series

The Troy sillimanite prospect is located east-southeast of Troy, Idaho. The mine site is southeast of Dry Ridge and approximately 1/4 mile north of Big Bear Creek (Figure 18). There are two adits within 50 yards of each other along the east bank of a small, unnamed Big Bear Creek tributary. Columbia River Basalt and contorted, gneissic, and schistose metamorphic rocks of the Belt Supergroup are the primary rock types of this region (Forrester, 1942).

Road Log: (refer to Figure 18)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 through Troy.

11.6 From the east side of Troy, continue following Highway 8

towards Deary.

17.5 Turn right on Granlund Road.

18.5 Turn left on Dry Creek Road.

20.5 Turn right on Hayden Road. Follow Hayden Road for approximately 1 mile across a field and down the draw.

21.5 Cross the creek and go approximately 1/4 mile and stop.

Walk down the creek bed approximately 50 yards. The main adit is about 20 ft. above the creek on the left side. There is a second adit 75 yards down stream but it is non-accessible owing to the murky water draining from the opening.

The main adit consists of three separate drifts, two bearing in an easterly direction and the third bearing in a northerly direction.

The head of the third adit is blocked by a winze that is approximately 40 feet deep. There are no additional adits extending from the winze.

This location would be best suited for a university petrology class field trip. Latah County map code is 17.

Figure 18: Map to Troy sillimanite prospect east of Troy,

Idaho.

Minerals Present:

Biotite Phlogopite

Brochantite Quartz

Garnet Sillimanite

Muscovite

Mineral Appearances:

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite mica occurs as relatively small (~ 5 mm) disseminated plates or platy aggregates in the sillimanite-mica schist. The individual plates are flexible and elastic with very pronounced vitreous luster. They also have perfect basal cleavage and are blackish-brown in color.

Brochantite - Cu4(SO4)(OH)6 (Hydrous Copper Sulfate)

Brochantite is present in granular form in veins in the adit, although some small prismatic crystals (~2 mm) are present. It is light blue-green in color with a vitreous to pearly luster and a light green streak. The brochantite is very weathered, very fragile, and difficult to identify in hand sample owing to its physical similarity to other copper sulfate and copper carbonate minerals. Identification of this mineral was verified by X-ray diffraction in the laboratory.

Garnet - (Fe,Mg)3Al2(SiO4)3 (Iron, Magnesium Aluminum Silicate)

The garnets present at this location have almandine/pyrope chemistry. They are present in schistose veins in the adit as large crystals (1 to 3 cm), and in the mica schist around the adit entrance in smaller sizes (1 to 5 mm). The samples from the veins exhibit distinct dodecahedral crystal form, have a hardness of 6.5 - 7.5, and vary in color from dark reddish-brown to purple. The smaller garnets in the schist are brighter red and less weathered than the ones found in the adit, but still have the distinctive crystal form. Positive identification was obtained through the use of X-ray diffraction in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite mica occurs as small (~5 mm) thin disseminated plates in the sillimanite-mica schist. These flexible, elastic plates exhibit perfect basal cleavage, prominent vitreous luster, and a silvery or yellowish-white color.

Phlogopite - K(Mg,Fe)3(AlSi3)O10(F,OH)2

(Hydrous Potassium Aluminum Silicate)

Phlogopite occurs as very small (~ 1 mm) six-sided plates in the sillimanite-mica schist. It displays perfect basal cleavage with vitreous or pearly luster and is yellowish-brown in color.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as small (1 to 3 mm) gray, granular masses in pegmatite dikes cross-cutting the schist. It can be identified by its hardness (7.0), lack of cleavage, vitreous luster, and pale gray to white color.

Sillimanite - Al2SiO5 (Aluminum Silicate)

Sillimanite occurs as long, slender, fibrous crystals within the mica- sillimanite schists and as individual crystals in veins located inside the adits. The crystals are 0.5 to 1.5 cm long and vary slightly in color from a yellowish-white in the veins to gray in the schist. The yellowish white sillimanite has been weathered and is very fragile, but the crystals in the schist have a hardness of 6 - 7 with a vitreous or pearly luster.

WHITE CROSS MINE

Legal Description: Ownership:

NW1/4, NW1/4, NW1/4, Craig Lewis % Cope R.

Sec. 24, T40N, R5W Gale Jr., & Elizabeth Bybell

Latah County, Idaho 2450 Moscow Mountain

Robinson Lake Quadrangle, Idaho Moscow ID 83843

7.5 Minute Series (Topographic) Phone: (208) 883-3666

Latah County Map Series

The White Cross mine is located approximately nine miles northeast of Moscow on the southern slope of Moscow Mountain near the head of Gnat Creek (Figure 19). The rocks at this location are all part of the Idaho Batholith. At this particular site there are numerous quartz veins occurring in the granodiorite.

Road Log: (refer to Figure 19)

0.0 Starting point is the intersection of U.S. Highway 95 and State

Highway 8 in Moscow; proceed east on Highway 8 towards Troy.

1.1 Turn left (north) on Mountain View Road.

2.7 Turn right on Moscow Mountain Road.

5.5 "Y" in the road; stay to the right.

5.7 "Y" in the road; stay to the left.

6.7 "Y" in the road; stay to the right.

7.5 "Y" in the road; turn to the left.

There is a blue iron gate across this private access road.

It is neccessay to have permission to go beyond this gate.

8.3 Stop! The White Cross mine is approximately 1/4 mile up

the trail to the left, and the old road is not suitable for

vehicles.

Figure 19: Map to White Cross mine northeast of Moscow,

Idaho.

The White Cross mine is a good location for students in junior high or high school, as well as university-level mineralogy and petrology classes. It is possible, however, to find most of the minerals found at this site along any of the roads in the immediate area. If this plan is used, it would be beneficial to all age groups. The Latah County map code is 18.

Minerals Present:

Albite Microcline/Albite (perthite)

Biotite Muscovite

Garnet Pyrite

Limonite Quartz

Mineral Appearances:

Albite (plagioclase) - NaAlSi3O8 (Sodium Aluminum Silicate)

Albite occurs as small prismatic or bladed crystals in the granodiorite. The crystals are commonly 1 to 2 mm long and 0.5 to 1 mm wide with striations visible, with the aid of a hand lens, on some fresh surfaces. Albite is hard (6.0 - 6.5) with nearly right angle cleavage, a vitreous luster, and a white streak. The color of albite varies, at this location, from a very pale green to a greenish-white. Positive identification was attained by the use of the X-ray diffractometer in the laboratory.

Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2

(Hydrous Potassium Aluminum Silicate)

Biotite occurs as foliated, platy aggregates and as individual thin sheets in the granodiorite. The crystals range in size from <1 mm in the granodiorite to 5 cm across in the pegmatites. Biotite can be identified by its perfect basal cleavage, vitreous luster, flexible sheets, and brownish-black color.

Garnet - (almandine-pyrope) - (Fe,Mg)3Al2(SiO4)3

(Iron Magnesium Aluminum Silicate)

The garnets found at this location have almandine/pyrope chemistry. The samples are in the pegmatite and display distinct dodecahedral crystal form, have a hardness of 6.5 - 7.5 and are bright red in color. The crystals are relatively small, ranging in size from 1 to 3 mm. Positive identification was obtained through the use to X-ray diffraction in the laboratory.

Limonite - FeO*OH*nH2O (Hydrated Iron Oxide)

Limonite is present in the form of earthy, porous masses and as a crustal material covering the granitic rocks and filling in the voids created by fracturing. The physical properties of limonite are highly variable owing to varying chemical composition and habit, but at this location it is yellowish-brown in color with a earthy luster, pale brown to yellow streak, and very fragile.

Microcline/Albite - (Perthite) (K,Na)AlSi3O8

(Potassium Sodium Aluminum Silicate)

This sample is not an individual mineral. It occurs as a product of exsolution with a potassium-feldspar-rich host mineral and sodium plagioclase lamella (layers). It is hard (6.0), shows distinct, nearly right angle cleavage, has a vitreous luster, a white streak and is white in color. The crystals are large, ranging in size from approximately 2 cm wide to as much as 5 cm long. Positive identification was attained by the use of the X-ray diffractometer and the Scanning Electron Microscope in the laboratory.

Muscovite - KAl2(AlSi3O10)(OH)2

(Hydrous Potassium Aluminum Silicate)

Muscovite occurs as foliated, tabular, pseudo-hexagonal crystals in the granodiorite. Some are as large as 5 to 8 cm across, although smaller crystals in the 1 to 5 cm range are more common. The muscovite has perfect basal cleavage in thin, flexible, elastic sheets. It is soft (2 - 2.5) and is primarily a yellow-brown color in thick, foliated books, but clear where found in thin sheets.

Pyrite - FeS2 (Iron Sulfide)

Pyrite occurs as very small striated cubes and compact granular aggregates. It can be distinguished from chalcopyrite by its higher hardness (6.0 - 6.5), black streak, and bright metallic luster. Pyrite is also a darker yellow color than chalcopyrite.

Quartz - SiO2 (Silicon Oxide)

Quartz is present as massive, microcrystalline masses in the igneous rocks, and as very small hexagonal crystals in the fractures and voids as a result of hydrothermal activity. It is also abundant throughout the tailings piles. The quartz that has been exposed and weathered is coated with a yellow or red-brown iron stain, whereas freshly broken samples are of the smoky-quartz or milky-quartz variety. It is hard (7.0), shows no cleavage but conchoidal fractures are evident, and has a vitreous luster.

REFERENCES CITED

Anderson, Alfred L., 1933, Genesis of the mica pegmatite deposits of

Latah County, Idaho: Economic Geology, Vol. 28, No.1.

Armstrong, R. L., Taubeneck, W. H., and Hales, P. O., 1977, Rb-Sr and

K-Ar geochronometry of Mesozoic granitic rocks and their Sr

isotopic composition, Oregon, Washington, and Idaho: Geological Society of America Bulletin, v. 88, p. 397-411.

Baksi, A. K., 1989, Reevaluation of the timing and duration of extrusion of the Imnaha, Picture Gorge, and Grande Ronde Basalts, Columbia River Basalt Group, in S. P. Hooper and Reidel editors, Volcanism and Tectonism in the Columbia River Flood Basalt Province: Geological Society of America Special Paper 239, p. 105-112.

Bickford, M. E., Chase, R. B., Nelson, B. K., Shuster, R. D., and Arruda, E. C., 1981, U-Pb studies of zircon cores and overgrowths, and

monazite: implications for age and petrogenesis of the

northeastern Idaho Batholith: Journal of Geology, v. 89, p. 433- 457.

Bitten, B. I., 1951, Age of the Potato Hill volcanic rocks near Deary,

Latah County, Idaho: University of Idaho Master's Thesis, 65 p.

Brown, J. C., 1976, Well construction and stratigraphic information:

Pullman test observation well, Pullman, Washington: Washington State University, College Engineering Research

Department, 76/15-6, 35 p.

Camp, V. E., 1976, Petrochemical stratigraphy and structure of the

Columbia River Basalt, Lewiston Basin area, Idaho-Washington:

Washington State University, Pullman, Ph. D. Dissertation,

201 p.

Camp, V. E., 1981, Geological studies of the Columbia Plateau; Part 2,

Upper Miocene basalt distribution reflecting source location,

tectonism, and drainage history of the Clearwater embayment,

Idaho: Geological Society of America Bulletin, v 92, p. 669-678.

Forrester, J. Donald, 1942, A sillimanite deposit near Troy, Latah

Co. Idaho: Idaho Bureau of Mines and Geology, Pamphlet 59.

Hamilton, W., and Myers, B. W., 1967, The nature of batholiths: United States Geological Survey Professional Paper 554-C,

29 p.

Harrison, J. E., 1972, Precambrian Belt basin of northwestern United

States: Its geometry, sedimentation, and copper occurrences:

Geological Society of America Bulletin, v. 83, p. 1215-1240.

Harrison, J. E., and Grimes, D. J., 1970, Mineralogy and geochemistry

of some Belt rocks, Montana and Idaho: United States Geological Survey Bulletin, 1312-0, 49 p.

Harrison, J. E., and Jobin, D. A., 1963, Geology of the Clark Fork

quadrangle Idaho-Montana: Geological Survey Bulletin 1141-K,

38 p.

Harrison, J. E., and Jobin, D. A., 1965, Geologic Map of the Packsaddle

Mountain Quadrangle, Idaho: United States Geological Survey

Quadrangle Map GQ-375, with text, 4 p.

Hietanen, A., 1963, Metamorphism of the Belt Series in the Elk River

-Clarkia area of Idaho: United States Geological Survey

Professional Paper 344C, 49 p.

Hietanen, A., 1968, Belt series in the region around Snow Peak and

Mallard Peak, Idaho: United States Geological Survey

Professional Paper 344E, 34 p.

Hooper, P. R., 1982, The Columbia River Basalts: Science, v. 215,

p. 1463-1468.

Hooper, P. R., and Webster, G. D., 1982, Geology of the Pullman, Moscow West, Colton, and Uniontown 7.5 minute quadrangles,

Washington and Idaho: State of Washington Department of

Natural Resources, Geologic Map GM-26.

Hooper, P. R., Webster, G. C., and Camp, V. E., 1985, Geologic map of the

Clarkston 15-minute quadrangle, Washington and Idaho: State of

Washington Department of Natural Resources Geologic Map,

GM-31, scale 1:48,000.

Hubbard, Charles R., 1957, Mineral resources of Latah County: Idaho

Bureau of Mines and Geology, County Report No. 2, 29 p.

Hustedde, Gail S., Strowd, William B., Mitchell, Victoria E., Bennett, Earl H., 1981, Mines and Prospects of the Pullman Quadrangle

Idaho: Idaho Bureau of Mines and Geology, Mines and Prospects Map Series.

Hyndman, D. W., and Williams, L. D., 1977, The Bitterroot lobe of the

Idaho Batholith: Northwest Geology, v. 6-1, p. 1-16.

Jones, R. W., 1982, Early Tertiary-Age Kamiah volcanics, north- central Idaho, in Bonnichsen, B., and Breckenridge, R. M., eds.,

Cenozoic Geology of Idaho: Idaho Bureau of Mines and Geology

Bulletin 26.

Nelson, B. K., 1981, U-Pb isotopic systematics in the northeast

border zone of the Idaho Batholith, Bitterroot Range, Montana:

Unpublished Master's Thesis, University of Kansas, Lawrence,

Kansas, 82 p.

Reid, R. R., Bittner, E., Greenwood, W. R., Ludington, S., Lund, K., Motzer, W. E., and Toth, M., 1979, Geologic section and road log

across the Idaho Batholith: Idaho Bureau of Mines and Geology,

Information Circular 34, 20 p.

Reid, R. R., Greenwood, W. R., and Nord, G. L., Jr., 1981, Metamorphic

petrology and structure of the St. Joe area, Idaho: Geological

Society of America Bulletin, Part 2, v. 92, p. 94-205.

Reid, R. R., Morrison, D. A., and Greenwood, W. R., 1973, The Clearwater orogenic zone: a relict of Proterozoic orogeny in

central and northern Idaho, in Belt Symposium: v. 1, Idaho

Bureau of Mines and Geology, p. 10-56.

Reidel, S. P., Tolan, T. L., Hooper, P. R., Beeson, M. H., Fecht, K. R.,

Bentley, R. D., and Anderson, J. L., 1989, The Grande Ronde

Basalt, Columbia River Basalt Group: Stratigraphic

descriptions and correlations in Washington, Oregon, and

Idaho, in S. P. Reidel and P. R. Hooper, editors, Volcanism and

Tectonism in the Columbia River Flood-Basalt Province:

Geological Society of America Special Paper 239, p. 21-54.

Savage, C. N., 1973, A geological field trip in Benewah and Whitman

Counties, Idaho and Washington, respectively, in Belt Symposium: v. 1, Idaho Bureau of Mines and Geology, p. 253- 307.

Shuster, R. D., and Bickford, M. E., 1985, Chemical and isotopic

evidence for the petrogenesis of the northeastern Idaho

Batholith: Journal of Geology, v. 93, p. 727-742.

Sterrett, D. B., 1923, The mica deposits of the United States:

United States Geological Survey Bulletin 740, p. 86-93.

Stoll, W. C., 1950, Mica and beryl pegmatites in Idaho and Montana:

Geological Survey Professional Paper 229, 64 p.

Swanson, D. A., Wright, T. L., Camp, V. E., Gardener, J. N., Helz, R. T.,

Price, S. M., Reidel, S. P., and Ross, M. E., 1980, Reconnaissance

geologic map of the Columbia River Basalt Group, Pullman and

Walla Walla quadrangles, southeast Washington and adjacent

Idaho: U.S. Geological Survey Miscellaneous Investigations Map

I-1139, scale 1:250,000.

Swanson, D. A., Wright, T. L., and Helz, R. T., 1975, Linear vent systems and estimated rates of magma production and eruption

for the Yakima Basalt on the Columbia Plateau: American

Journal of Science, v. 275, p. 877-905.

Swanson, D. A., Wright, T. L., Hooper, P. R., and Bentley, R. D., 1979,

Revisions in staratigraphic nomenclature of the Columbia River Basalt Group: United States Geological Survey Bulletin

1457-G, 59 p.

Tolan, T. L., Reidel, S. P., Beeson, M. H., Anderson, J. L., Fecht, K. R., and

Swanson, D. A., 1989, Revisions to the estimates of the areal

extent and volume of the Columbia River Basalt Group in Reidel,

S. P., and Hooper, P. R., eds., Volcanism and tectonism in the

Columbia River flood-basalt province: Boulder, Colorado,

Geolobical Society of America Special Paper 239, 20 p.

Tullis, E. L., 1944, Contributions to the geology of Latah County, Idaho: Geological Society of America Bulletin, v. 55, p. 131- 164.

Webster, G. D., and Nunez, L., 1980, Geology of the steptoes and

Palouse Hills of eastern Washington, A roadlog of the area

south of Spokane, Washington, Roberts, S. and Fountain, D.,

eds., Tobacco Root Geological Society Field Conference 1980,

92 p.

APPENDIX A

BELT SUPERGROUP ROCKS

Background Information

Meta-sedimentary rocks of the Belt Supergroup extend from western Montana through northern Idaho and into bordering parts of Washington and British Columbia. Lithologically, the rocks of the Belt Supergroup can be described as a thick sequence of alternating argillite, siltite, and quartzite with minor carbonate. The effects of low grade metamorphism are reflected in the recrystallized textures, but the metamorphism has not destroyed the sedimentary features at every outcrop.

From bottom to top, the major units of the Belt rocks in northern Idaho are: Prichard, Burke, Revett, St. Regis, Wallace, Striped Peak, and Libby Formations. The Burke, Revett, and St. Regis Formations are members of the Ravalli Group and the Striped Peak and Libby Formations constitute the Missoula Group. The rocks of the Belt Supergroup attain a maximum thickness of 67,000 feet (Harrison, 1972).

Rocks of the Belt Supergroup range from approximately 1,450 to 850 million years old; and the sediments forming them were deposited in what may have been a slowly subsiding marginal re-entrant that trends north to northwest, commonly referred to as the Belt Basin (Harrison, 1972). South and southwest of the basin, along the St. Joe River drainage, progressive metamorphism of the Belt rocks has made identification of the units much more difficult. Regionally, metamorphism increases from zeolite facies in the northeast to amphibolite facies in the southwest where pre-Belt and Belt terrains encounter the Idaho Batholith (Hietanen, 1963, 1968; Harrison, 1972; Reid and others, 1973; Reid and others, 1981). The degree of metamorphism also increases downwards in sections where siltite, argillite, and quartzite have been transformed into recrystallized, foliated schist and quartzose gneiss. However, in most places even with the high metamorphism, the units can be mapped separately (Hietanen, 1963, 1968; Harrison, 1972; and Reid and others, 1981).

There is so little variation in rock type, grain size, and color that, to many workers, the Belt rocks are monotonous in appearance (Harrison and Grimes, 1970). However, where metamorphism has not been intense, sedimentary structures such as cross-beds, ripple marks, parallel laminations, load casts, mud cracks, and stromatolites are well preserved. These structures, where present, have been used to help define rock units and to interpret depositional environments.

The Belt Supergroup consists of the following five basic rock types: (a) very fine-grained to fine-grained quartzite and arkosic quartzite; (b) siltite and argillitic siltite; (c) laminated black argillite and white or green siltite; (d) argillite and silty argillite; and (e) carbonate rocks. Nearly identical rock types commonly occur in several formations or in at least two members of a single formation. Green to gray-green, thin-bedded to laminated siltite or argillitic siltite is abundant throughout most of the sequence and, therefore, is the least useful of all the rock types for identification of stratigraphic position. Differences among the similar rock units are subtle, but many of these differences are useful for mapping.

Individual Latah County Formations

There are three specific formations thought to be present in north-central Latah County from the Laird Park area northward to and beyond the Benawah-Latah county line. In the immediate Laird Park vicinity, approximately 3.5 miles east and 2 miles southeast of Harvard, rock types similar to the Wallace and Revett Formations exist.

The Wallace Formation is about 10,200 feet thick (Harrison and Jobin, 1965). The formation is the most heterogeneous and is the principal carbonate-bearing formation of the entire Belt sequence. The common rock types are: (a) black and white or green thinly interlaminated argillite and siltite; (b) green siltite thinly interbedded with argillitic green siltite; (c) blue-gray laminated dolomitic limestone; (d) greenish-gray, very thin bedded dolomitic or calcareous siltite and dolomitic or calcareous argillitic siltite; (e) black laminated silty argillite; (f) white laminated dolomitic quartzite; and (g) laminated waxy green argillite. Outcrops located along the Palouse River Road, from 0.5 to 1.0 mile southeast of the junction with State Highway 6, contain banded argillite and silty argillite along with calcareous, dolomitic, and scapolitic features. The white blebs and masses of scapolite are also indicators of the Wallace Formation. Scapolite is a complex of potassium, calcium, aluminum silicate mineral associated with metamorphosed calcium-rich rocks.

An outcrop believed to belong to the Revett Formation is located approximately 1.7 miles from the State 6 junction on the left hand side of the road east of Laird Park. The Revett Formation is about 2,000 feet thick (Harrison and Jobin, 1963). Lithologically it is the most homogenous unit of the Belt Supergroup. The quartzite is mostly fine-grained and relatively pure. It is distinguishable by its beds of blocky white to gray, cross-bedded quartzite. Laminated green argillite is also common in the Revett. The sedimentary structures include cross-beds, ripple marks, mudcracks, and mud-chip breccias. The exposure at this location is dominated by blocky, gray quartzite. The quartzite is cross-laminated with bands which may follow depositional bedding laminations. The outcrop displays an excellent cross-sectional view of a large channel approximately twenty feet across. A fault is exposed on the western end of the exposure where the quartzite is highly brecciated across a twenty-five foot thick zone.

The third formation thought to exist in Latah county is the Libby Formation. This formation is present mainly in the extreme north-central part of the county south of the North South Ski Bowl. The Libby Formation in this area is an incomplete sequence as its top has been removed by erosion. Exposed portions of this formation consist of laminated black argillite and white siltite, green to gray cherty argillite and siltite that contains carbonate minerals, green to tan silty limestone and dolomite, and a few beds of calcareous and cherty stromatolites and oolites.

Mud cracks and ripple marks are abundant throughout the formation, and mud-chip breccia is characteristic of the carbonate-bearing siltites and argillites. Chert occurs as pale green layers and lenses in laminated green argillite and siltite, as pale green chips in some of the mud-chip breccias, and as black layers or irregular patches that transect layering in the stromatolites and oolites. Oolites, where present, are in beds just below stromatolitic units.

IDAHO BATHOLITH

Background Information

The Idaho Batholith, which occupies much of central Idaho, is approximately 250 miles long and 80 miles wide and it surrounded by regionally metamorphosed rocks (Hamilton and Myers, 1967). The batholith consists of a complex group of plutons which range in age from Cretaceous to Early Tertiary (Armstrong and others, 1977; Bickford and others, 1981). The large body can be subdivided into two separate lobes, the northern Bitterroot lobe and the southern Atlantic lobe. Both regions are underlain by massive granite, granodiorite, and quartz diorite. According to Shuster and Bickford (1985), the most voluminous rock is a weakly foliated, medium-grained two-mica granite with K-feldspar megacrysts. In numerous areas, considerable schist and gneiss are interspersed with the granitic rocks.

The contacts between country rocks and the batholith are, in places, wide and generally gradational changing from granite to gneissic granite. The general lithologies and the sequences of the country rocks suggest correlation with the Prichard Formation, Ravalli Group, and the Wallace Formation of the Belt Supergroup (Hyndman and Williams, 1977; Reid and others, 1979). These rocks range from metasedimentary rocks to sillimanite-grade metasedimentary country rocks. Inclusions are common in the granites adjacent to contacts, and the abundance decreases away from those contacts (Shuster and Bickford, 1985).

The main phase of igneous intrusion ranges in age from 66 million years to 46 million years (Nelson, 1981). Shuster and Bickford (1985) reported a date of 46 m.y. for one of the youngest intrusions, and Webster and Nunez (1981) reported a date of 67.8 m.y. for granitic rocks near Viola, Idaho north of Moscow.

The origin of the Idaho Batholith is controversial. Shuster and Bickford (1985, p. 738) stated that their date "indicates that the source of the granite was not the exposed intruded country rocks, but was depleted lower crust that is heterogeneous, Proterozoic in age, aluminum rich, and has garnets as a residual phase."

Latah County Intrusions

In Latah County there is a large area of intrusive rocks that extends across the county from the northeastern corner to the Idaho and Washington state line, north and south of Moscow. These rocks underlie such areas as the Thatuna Hills, Paradise Ridge, Bald Butte, and the Palouse Range. Because this plutonic mass is isolated from, and appears to be independent of the Idaho Batholith, Tullis (1944) referred to these rocks as the Thatuna Batholith. There has not been any detailed work on these rocks since Tullis, but here they are considered to be related to the Idaho Batholith. The dates of 69.8 m.y. and 67.8 m.y. respectively, for rocks from the Palouse Range (Webster and Nunez, 1981) and from Bald Butte (Hooper and Webster, 1982) place them in the Cretaceous and within the age range of the Idaho Batholith.

Tullis (1944) reported that granodiorite, adamellite, tonalite, and granite each makeup considerable masses and form the principal intrusions. Typical rocks are light-gray and equigranular but the textures may be gneissic, porphyritic, and pegmatitic. The principal visible minerals are quartz, feldspar, and biotite. Muscovite is common in places, as well as garnet and epidote. Hornblende is present in the quartz-deficient rock types. Microcline, orthoclase, and albite are the principal feldspars. Other lesser rocks include diorite, aplite, granodiorite porphyry and lamprophyre dikes.

Granite pegmatite and aplite dikes are locally present and, at times, have been mined for mica in the Avon district near Deary, Idaho. The pegmatite is in contact with schist and minor gneiss of the Belt Supergroup rocks. The beds of schist are gray or silvery white that weather to an iron brown color. Layers of mica gneiss are interbedded with the schist. The introduction of aplite and pegmatite presumably accompanied the intrusion of the underlying Idaho Batholith because narrow dikes and sills cut both the schist and gneiss at several localities.

According to Stoll (1950), there were about 100 pegmatite dikes and sills wider than one foot exposed in trenches, outcrops, pits, and underground workings in the Avon district. The pegmatite seems to be unevenly distributed in the area. Individual bodies lie closely spaced in groups or in a series separated by relatively broad tracts of metamorphic rock containing few pegmatites. Stoll (1950) reported that the district included about 18 mines and prospects that produced mica sheets in quantities ranging from a few pounds to thousands of pounds. The last recorded production, that Stoll was aware of, occurred from 1943 - 1945 when the cost of shipping mica was assumed by the government. In addition to mica, small quantities of beryl were also mined (Stoll, 1950).

There are numerous reports on the Avon district pegmatites (Sterrett, 1923; Anderson, 1933; Forrester, 1942; and Stoll, 1950); however, modern research has not been done on either the pegmatites or the underlying batholith.

POTATO HILL VOLCANICS

Background Information

Potato Hill Volcanics consist of Early Tertiary-aged rhyolitic to dacitic lava flows and flow-breccia. The best exposure occurs on Potato Hill located approximately 0.5 mile north of Deary in east-central Latah County. Very little published information on these rocks is available, and good exposures of the sequence are rare.

The Potato Hill volcanic rocks rest on an erosion surface cut into granitic rocks of the Idaho Batholith (Jones, 1982). These rocks are predominately Cretaceous granodiorite and are known as the Thatuna Batholith (Bitten, 1951). The similarity between the granodiorite and intrusive clasts contained in the flow-breccias is evidence for a post-Idaho Batholith age for the Potato Hill volcanic rocks. Basalt of the Columbia River Basalt Group overlies the Potato Hill volcanics all around the flanks of Potato Hill. No clasts of Columbia River Basalt have been noted in the flow-breccias.

The Potato Hill volcanics can be divided into a lower porphyritic member and an upper flow-breccia member. The lack of exposures prohibits a thickness estimate for the lower member, although Tullis (1944) estimated it to be 200 to 300 feet thick. The upper flow-breccia member forms the bulk of Potato Hill and has an estimated thickness of approximately 1000 feet (Bitten, 1951; Tullis, 1944).

The lower member consists of porphyritic lava flows which are distinguished from the upper member by a general lack of lithic fragments, common presence of flow-layering, and a general lighter color. Compositionally the porphyritic flows were reported to be mainly rhyolite, rhyodacite, and dacite (Bitten, 1951). The lava flows are typically lavender or grayish-white but may be pinkish or brownish-gray. The flows contain between 3% and 10% phenocrysts set in a dense aphanitic groundmass. Locally the flows also contain 1% to 2% lithic fragments. The phenocrysts are predominately 1 mm to 3 mm long milky-white feldspars, with plagioclase being slightly more abundant than K-feldspars (Bitten, 1951). Rounded, anhedral, quartz grains, ranging in size from 0.25 mm to 2.0 mm in diameter, make up the remaining phenocrysts.

Outcrops of the lower member weather dark red-brown and are locally stained with iron-oxides, especially along the fractures. Orientation of the fractures is highly variable, and Bitten (1951) described the flows as sheeted masses. Where the flows crop out, flow layering can be determined with close inspection. It can be distinguished by closely spaced, alternating light and dark laminae or bands. These laminae are generally 0.25 to 2.0 millimeters thick. The laminae are subparallel and may be wavy. Individual laminae are observed to wrap around phenocrysts and rare lithic fragments.

The upper member consists of an inhomogeneous sequence of dense, dark flow-breccia with distinctive igneous and metamorphic clasts and intercalated lithic-poor lava flows. The flow-breccia is generally matrix-supported and contains variable proportions of angular to rounded clasts of volcanic, intrusive, and metamorphic origin. The matrix is black or brown-gray, devitrified glass and cryptocrystalline material (Bitten, 1951). Although the upper member is dark colored, Bitten (1951) suggested that the phenocryst mineralogy indicates a dacitic to rhyodacitic composition for the flow-breccia.

Hand specimens of this member contain between 5% and 20% lithic fragments and 5% to 10% phenocrysts scattered throughout the matrix. Phenocrysts in the matrix are difficult to distinguish from small lithic fragments or other foreign inclusions. Translucent or white, anhedral to subhedral feldspar phenocrysts are generally 0.5 mm to 2.0 mm in length. The feldspar appears less altered than in the porphyritic flows. Translucent plagioclase may have visible cleavage planes. Potassium feldspar has a whitish color and appears to be slightly less abundant than plagioclase. The anhedral clear crystals range from 0.50 mm to 1.0 mm in diameter.

The lithic content of the flow-breccia varies from as high as 50% at an exposure near Bovill, Idaho to 1% in some of the Potato Hill flows. The 1 cm to 10 cm size clasts are generally rounded and generally free of fractures. The volcanic fragments are considered to be the most abundant, followed by intrusive and metamorphic fragments. The volcanic fragments are dark-gray to gray, porphyritic, and closely resemble the porphyritic rocks of the lower member. The light colored intrusive fragments give the flow-breccia a distinctive "polka dot" appearance. Bitten (1951) reported that these fragments are mainly granodiorite. Metamorphic rock fragments are less conspicuous than the intrusive fragments, are fine-grained, and have a tan-orange color. It is possible they are clasts from the Belt Supergroup.

The flow-breccia member is more resistant than the lower member and forms rugged outcrops. Although the outcrops appear massive, flow-layering is locally evident by crude alignment of lithic fragments or rare gas cavities. It is common to note weathered-out horizons that recede back into the outcrops. These horizons may represent flow contacts which, if correct, may indicate that the individual flows ranged from 3 feet to 30 feet thick. No sedimentation or oxidation has been noted along these contacts.

No conclusive evidence regarding the origin of the Potato Hill volcanic rocks has been noted. The unconformable relation between the upper and lower members suggests that the two members may not be related to the same eruptive phase. Bitten (1951) suggested that the Potato Hill flows were caused by relatively quiet eruptions from one or more fissures in the Potato Hill vicinity. The lack of interbeds and oxidized flow contacts would suggest that the flows were probably erupted in rapid succession.

The fact that the upper member dips to the west at Potato Hill and the east at Cherry Butte makes it tempting to agree with Bitten (1951) that the area is a vent. However, the eastward dipping rocks that make up Cherry Butte can be explained by the presence of a northwest-trending fault located in the Brush Creek drainage, which may be why the lower member is present 500 feet higher on the Cherry Butte side.

A vent origin is also disputed by the absence of pyroclastic features and by the nature of the lithic fragments in the flow-breccia. The rounded fragments and weakly fractured nature of the clasts in the flow-breccia suggest that they were passively incorporated into the flow. If Potato Hill was a vent, pyroclastic features and more angular and fractured clasts should be present. Until additional work is done on the Potato Hill rocks, the conclusion is they represent two stages of post-Idaho Batholith and pre-Columbia River Basalt eruptions that accumulated more than 1000 feet of rhyolite, dacite, and rhyodacite volcanism, and the upper member (second stage) may represent numerous closely spaced events.

COLUMBIA RIVER BASALT GROUP

Background Information

The Columbia River Basalt Group erupted from fissures during an 11-million year period of the Miocene (6 million to 17 million years ago). The bulk of the basalt was erupted in the first 1.5 million years (Baski, 1989) over a 163,700 km2 area (Tolan and others, 1989) that included most of eastern Washington, much of northern Oregon, and significant parts of west-central Idaho. The accessibility of the Columbia River basalt in this broad area makes it amenable to detailed stratigraphic, chemical, magnetic, and petrographic studies.

Most flows of the Columbia River Basalt Group may be identified by their chemical composition. New techniques of rapid chemical analysis and magnetic polarity, in conjunction with field mapping, have enabled scientists to establish a detailed stratigraphic succession for the Columbia River Basalt Group. Based on the stratigraphy, it has been possible to clarify the physical and chemical evolution of the basalt magma, to correlate individual flows with their feeder dikes, and to reconstruct the magnitude of the eruptions.

The maximum exposed thickness of the Columbia River Basalt Group is 1,500 meters, but basaltic rocks have been reported from drill cores as deep as 3,000 meters near the center of the plateau (Hooper, 1982). The total thickness of the basalt, based on estimates of the greatest known thickness for each formation, is more than 2,500 meters. The Columbia River Basalt Group fills a shallow basin; it is thickest at the center (Pasco Basin) and thins toward the margin. The number of flows identified on the plateau is between 120 and 150 (Hooper, 1982). Individual flows are as much as 122 meters thick and average 15 to 30 meters thick. Their areal extent ranges from small spatter cones at source vents to major flows that cover a significant part of the Columbia Plateau with volumes as large as 700 cubic kilometers. The flows were erupted from north-northwest to south-southeast fissures concentrated in the southeastern part of the plateau where dikes cut through older lava flows and the surrounding pre-basaltic rocks (Swanson and others, 1975).

From the base upward, the Columbia River Basalt Group in the Moscow-Pullman-Lewiston area is subdivided into the Imnaha, Grande Ronde, Wanapum, and Saddle Mountains Formations. Near Moscow, Idaho most basalt outcrops are the Priest Rapids Member of the Wanapum Formation. The contact between the Wanapum and underlying Grande Ronde Formation has been mapped along Paradise Creek west of Pullman (Hooper and Webster, 1982). This contact has also been identified by Brown (1976) in a test well between Moscow and Pullman at a depth of 30 meters. All of the above mentioned formations are present in the Lewiston-Clarkston area. Dike and vent materials are visible at numerous locations in northern Idaho and southeastern Washington.

Basalt flows of the Grande Ronde, Wanapum, and Saddle Mountains Formations range in thickness from less than 30 centimeters to more than 100 meters. The flows record ponding in valleys, in structurally controlled basins that developed during volcanism, and in narrow canyons eroded into older flows. The intracanyon flows are common in the Saddle Mountains Basalt. All of the flows generally show evidence of ponding based on the columnar-jointed features exhibited by basalt. Columnar joints apparently form only under static cooling conditions.

Flows that cooled under static conditions contracted and developed a characteristic jointing habit, which include colonnades and entablatures. Colonnade refers to the larger columns that make up the base of the flow. Entablatures are the smaller columns at the upper part of a flow and generally constitute approximately 20% of the thickness of the flow, but it can be all of the flow or none of it. Most entablature columns are segmented by irregular cross joints, causing the columns to easily break into smaller (fist sized) pieces. The colonnade-entablature contact may be sharp, and the change generally occurs within 1 meter. These contacts are traceable, in some areas, for several kilometers. The columns in the colonnade range from 30 centimeters to 5 meters in diameter and are 15 to 30 feet in length. Most columns are straight, but curved ones are not uncommon.

Individual Flows

Introduction:

The Columbia River Basalt Group has been subdivided into a large number of flows, members, and formations. (Swanson and others, 1979). The term "flow" is used for individual cooling units. The term "member" is used to define a flow or group of flows that can be distinguished from all others by its unique set of physical and chemical properties. These criteria include stratigraphic position, petrographic assemblage, magnetic properties, and chemical composition.

From the base upward, the Columbia River Basalt Group in the Moscow-Pullman-Lewiston area is subdivided into the Imnaha, Grande Ronde, Wanapum, and Saddle Mountains Formations. Brief descriptions of these formations are given on the following pages. Particular emphasis is given to the Grande Ronde and Wanapum Formations because they are the predominate formations present in Latah County. For more information regarding these formations and their associated members, see Dr. John Bush at the University of Idaho.

Imnaha Basalt

The flows of the Imnaha Basalt conformably underlie the Grand Ronde Basalt. Generally they are medium to coarse grained with phenocrysts of plagioclase ranging in length from 0.5 cm to 2.5 cm. Exposures are characterized by extensive weathering. Most flows have normal magnetic polarity. Because these flows were the first to fill in the prebasalt topography, they vary widely in thickness.

Grande Ronde Basalt

The Grande Ronde Basalt is a thick sequence of flows that occur over much of the Columbia River Plateau. The flows are fine-grained and petrographically obscure. Individual flow thickness ranges between 1 and 50 meters and covers hundreds of square kilometers. Total thickness reaches over 1000 meters in some places. The member has been divided into four units (Hooper and others, 1985) on the basis of magnetic differences and has been dated between 15.6 m.y and 17.0 m.y. (Reidel and others, 1989). From the base upward, these units are referred to as N1, R1, N2, and R2. The Grande Ronde Basalt has a narrow range of chemical composition and relatively uniform lithology. Reidel and others (1989) used chemical compositions with paleomagnetic polarity, lithology, and stratigraphic position to subdivide the formation. They were able to split the four magnetostratigraphic units into seventeen informal units that can be mapped and recognized across the Columbia Plateau.

Wanapum Formation

The Wanapum Formation consists primarily of the Priest Rapids Member in Latah County. The Priest Rapids Member is a coarse-grained flow with plagioclase (predominately labradorite) and olivine phenocrysts. The member occurs as an extensive flow or as flows of relatively uniform thickness over much of the plateau but is thicker in the Lewiston basin than it is in the Moscow area (Hooper and others, 1985). Major feeder dikes occur in northern Idaho (Camp, 1981). These dikes presumably fed the flows, which moved westward into the central Columbia Plateau as sheetfloods (Swanson and others, 1980). In the eastern part of the plateau, this flow overlies a dark-brown, well-developed saprolite (clay-rich decomposed rock). The flows have reversed magnetic polarity (Swanson and others, 1979).

Saddle Mountains Formation

The Saddle Mountains Formation consists of numerous flows and interbeds. The most common members of this formation in this area from oldest to youngest are: (a) the Wilbur Creek Member; (b) the Pomona Member; (c) the Elephant Member; and (d) the Lower Monumental Member.

These members are the predominant flows of the ancestral Snake River canyon in the Lewiston basin. Remnants of these flows extend from the top of the Lewiston grade (Swanson and others,1975) to as far west as Devils Canyon in southeastern Washington (Swanson and others, 1980).

In hand sample, the basalt is dark gray, fine to medium-grained, and contains small phenocrysts or laths of plagioclase. Clinopyroxene and olivine are also visible in an opaque, glassy matrix.

APPENDIX B

Minerals and Locations

Actinolite Emerald Creek Road (FSR #447)

Stops #1 & #2

Gold Hill Loop

Stops #1, #2, #3, & #4

Harvard Park

Palouse Divide Road (FSR #377)

Stops #6, #7, & #8

Albite (plagioclase) Mica Mountain muscovite mine

White Cross mine

Albite/Microcline Gold Hill prospect

(Antiperthite)

Ankerite Gold Bug prospect

Apatite Genesee (Little Potlatch Creek)

Gold Hill Loop

Stop #3

Aragonite Basalt quarry on Palouse River

near Potlatch

Harvard-Deary Cutoff

basalt quarry

Arsenopyrite Gold Bug prospect

Mizpah mine

Augite Gold Bug prospect

Azurite Gemmill prospect

Mizpah mine

Beryl Mica Mountain muscovite mine

Biotite Emerald Creek Garnet Company

mining site

Emerald Creek Road (FSR #447)

Gemmill prospect

Genesee (Little Potlatch Creek)

Gold Bug prospect

Gold Hill Loop

Mica Mountain muscovite mine

Palouse Divide Road (FSR #377)

Troy sillimanite prospect

White Cross mine

Bornite Gemmill prospect

Mizpah mine

Brochantite Mizpah mine

Troy sillimanite prospect

Calcite Basalt quarry on Palouse River

near Potlatch

Gemmill prospect

Harvard-Deary Cutoff

basalt quarry

Harvard Park

Troy-Deary Gun Club basalt quarry

Chabazite Nirk basalt quarry

Chalcocite Mizpah mine

Chalcopyrite Gemmill prospect

Gold Bug prospect

Gold Hill prospect

Mizpah mine

Copper Gemmill prospect

Mizpah mine

Corundum Genesee (Little Potlatch Creek)

Cuprite Mizpah mine

Diopside Emerald Creek Road (FSR #447)

Epidote Gold Hill Loop

Stop #4

Harvard Park

Ferroactinolite Gold Hill prospect

Fluorapatite Palouse Divide Road (FSR #377)

Garnet (almandine) Emerald Creek Garnet Company

mining site

FSR digging area

Emerald Creek Road (FSR #447)

Garnet (almandine/pyrope) Genesee (Little Potlatch Creek)

Mica Mountain muscovite mine

Troy sillimanite prospect

White Cross mine

Garnet (grossular/andradite) Gemmill prospect

Goethite Basalt quarry on Palouse River

near Potlatch

Gold Bug prospect

Gold Hill Loop

Stop #1

Troy-Deary Gun Club basalt quarry

Gold Gold Hill prospect

Hematite Basalt quarry on Palouse River

near Potlatch

Gold Bug prospect

Gold Hill Loop

Stop #1

Gold Hill prospect

Harvard-Deary Cutoff

basalt quarry

Mizpah mine

Hornblende Genesee (Little Potlatch Creek)

Gold Hill Loop

Stop #3

Kyanite Emerald Creek Garnet Company

mining site

Emerald Creek Road (FSR #447)

Labradorite (plagioclase) Gemmill prospect

Harvard-Deary Cutoff

basalt quarry

Nirk basalt quarry

Limonite Basalt quarry on Palouse River

near Potlatch

Gemmill prospect

Gold Bug prospect

Gold Hill Loop

Stop #5

Harvard-Deary Cutoff

basalt quarry

Mizpah mine

Palouse Divide Road (FSR #377)

Stops #6, #7, & #8

White Cross mine

Malachite Gemmill prospect

Gold Hill Loop

Stop #5

Mizpah mine

Microcline Genesee (Little Potlatch Creek)

Gold Hill Loop

Stop #3

Palouse Divide Road (FSR #377)

Stops #1, #2, & #3

Microcline/Albite (perthite) Gold Bug prospect

Gold Hill prospect

White Cross mine

Muscovite Emerald Creek Garnet Company

mining site

Emerald Creek Road (FSR #447)

Genesee (Little Potlatch Creek)

Mica Mountain muscovite mine

Palouse Divide Road (FSR #377)

Stops #3, #4, & #5

Troy sillimanite prospect

White Cross mine

Nontronite Harvard-Deary Cutoff

basalt quarry

Olivine Harvard-Deary Cutoff

basalt quarry

Opal Basalt quarry on Palouse River

near Potlatch

Harvard-Deary Cutoff

basalt quarry

Highway 3 roadcut near Kendrick

Troy-Deary Gun Club basalt quarry

Phlogopite Mica Mountain muscovite mine

Palouse Divide Road (FSR #337)

Stops #1 & #2

Troy sillimanite prospect

Pyrite Gemmill prospect

Genesee (Little Potlatch Creek)

Gold Bug prospect

Gold Hill Loop

Stop #1

Gold Hill prospect

Mizpah mine

Nirk basalt quarry

White Cross mine

Pyrolusite Gold Bug prospect

Highway 3 roadcut near Kendrick

Palouse Divide Road (FSR #377)

Stops #6, #7, & #8

Pyrrhotite Mizpah mine

Quartz Emerald Creek Garnet Company

mining site

Emerald Creek Road (FSR #447)

Gemmill prospect

Gold Bug prospect

Gold Hill Loop

Stops #1 & #5

Gold Hill prospect

Harvard Park

Mica Mountain muscovite mine

Mizpah mine

Palouse Divide Road (FSR #377)

Stops #1, #2, #3, #4, & #5

Troy sillimanite mine

White Cross mine

Scapolite Emerald Creek Road (FSR #447)

Stops #1 & #2

Harvard Park

Siderite Basalt quarry on Palouse River

near Potlatch

Troy-Deary Gun Club basalt quarry

Sillimanite Emerald Creek Garnet Company

mining site

Emerald Creek Road (FSR #447)

Troy sillimanite prospect

Staurolite Mizpah mine

Sulfur Gold Hill prospect

Titanite (sphene) Gold Hill Loop

Stop #6

Gold Hill prospect

Palouse Divide Road (FSR #337)

Stops #1 & #2

Tourmaline Mica Mountain muscovite mine

Mizpah mine

Tremolite Palouse Divide Road (FSR #337)

Stops #6, #7, & #8

Zinnwaldite(?) Mizpah mine

Zircon Genesee (Little Potlatch Creek)