Clara Creek

The Clara Creek is a mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Clara Creek

Commodity

Secondary: Chromium
Secondary: Gold

Location

State: Alaska
District: Goodnews Bay

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Placer PGE-Au

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chromite
Ore: Gold
Ore: Ilmenite
Ore: Magnetite
Ore: Sperrylite

Comments

Comment (Exploration): Status = Active?

Comment (Reference): Primary Reference = Mertie, 1940

Comment (Workings): Workings / Exploration = Platinum was discovered and small-scale placer mining started in 1928. At least some mining took place every year thereafter to 1940 (Fechner, 1988). A dragline was installed in 1935 and larger scale operations exhausted the 200- to 250-foot wide paystreak by 1940 (Mertie, 1969, p. 77).

Comment (Geology): Geologic Description = Clara Creek, a west tributary to upper Salmon River, flows eastward from headwaters on the north end of the Red Mountain ultramafic pluton. It has been placer mined over about 1.4 miles of its 1.5 mile length. Platinum was discovered and placer mining started in 1928. At least some mining took place every year thereafter to 1940 (Fechner, 1988). A dragline was installed in 1935 and larger scale operations exhausted the 200- to 250-foot wide paystreak by 1940 (Mertie, 1969, p. 77). Gravels in Clara Creek were 10 to 12 feet thick and except for 2 or 3 feet of vegetation-rich material and the upper 2 or 3 feet of gravel, the remainder of the alluvial section was platinum-bearing and mineable (Mertie, 1940). The gravel is subangular, mostly 3 to 4 inches in diameter, and contains cobbles and erratic boulders to 3 or 4 feet across in upper gravel horizons. Higher platinum grades were concentrated on bedrock, in the gravels within a few feet of bedrock, and up to 3 or 4 feet in deeply weathered and fractured bedrock. Mertie (1940) reported that platinum grades were as high as 0.08 ounce per cubic yard but that they were probably generally lower, perhaps averaging 0.02 ounce of platinum per cubic yard. The platinum in Clara Creek is generally fine grained but nuggets up to 2 ounces in size were recovered. Analysis of platinum-bearing concentrate shows 73.29 percent Pt, 5.90 percent Ir, 0.69 percent Os, 0.42 percent Rh, 0.56 percent Pd, 1.01 percent Au, and 18.00 percent impurities (Mertie, 1940, p. 79). The mean of analyses of 6 Pt-rich samples recalculated free of impurities was 88.61 percent Pt, 6.05 percent Ir, 0.97 percent Os, 0.09 percent Ru, 1.01 percent Rh, 0.40 percent Pd, and 2.87 percent Au (Mertie, 1976). Concentrate from one cleanup contained 6.179 ounces gold, 36.098 ounces Ir, 440.421 ounces Pt, 4.221 ounces Os, 0.795 ounce Ru, and 2.569 ounces Rh (Roehm, 1937). A U. S. Bureau of Mines sample from the unmined upper part of the creek contained 0.034 ounce of of PGM per cubic yard; microprobe analysis of this sample showed it to contain 1.6 percent Rh, 0.5 percent Ru, 83 percent Pt, 3.8 percent Ir, 1.0 percent Os, and 8.1 percent Fe (Fechner, 1988, p. 71). Fechner (1988) reported four platinum-bearing phases in this sample: iron-platinum alloy with 8 to 30 percent iron, iron-platinum alloy with minor osmiridium inclusions, hollingsworthite, and sperrylite. The unmined part of upper Clara Creek is estimated to be 900 feet long, 75 feet wide, and 2 feet thick; it contains about 5,000 cubic yards of material having a possible grade of 0.034 ounce of PGM per cubic yard (Fechner, 1988, p. 71). The bedrock of Clara Creek is mostly sheared and deeply weathered chert, quartzite, tuffaceous rocks, and chlorite schist that, in the upper part of the creek are in contact with ultramafic rocks of the Jurassic Red Mountain pluton (Mertie, 1940; Hoare and Coonrad, 1978). The country rocks are included in a regional sedimentary and volcanic assemblage that ranges in age from Paleozoic to Mesozoic (Hoare and Coonrad, 1978).

Comment (Deposit): Model Name = Placer PGE-Au (Cox and Singer, 1986; model 39b)

Comment (Production): Production Notes = Fechner (1988) estimates that a total of 3,590 ounces of PGM were recovered from about 500,000 cubic yards of alluvial material on Clara Creek.

Comment (Geology): Age = Quaternary.

Comment (Reserve-Resource): Reserves = The unmined part of upper Clara Creek is estimated to be 900 feet long, 75 feet wide, and 2 feet thick; it contains about 5,000 cubic yards of material having a possible grade of 0.034 ounce of PGM per cubic yard (Fechner, 1988, p. 71). There are an estimated 500,000 cubic yards of tailings in Clara Creek that contain 0.0080 ounce of PGM per cubic yard (Fechner, 1988, p. 28).

References

Reference (Deposit): Mertie, J.B., Jr., 1976, Platinum deposits in the Goodnews Bay district, Alaska: U.S. Geological Survey Professional Paper 938, 42 p.

Reference (Deposit): Cobb, E.H., 1980, Summaries of data and lists of references to metallic and selected nonmetallic mineral deposits in fifteen quadrangles in southwestern and west-central Alaska: U.S. Geological Survey Open-File Report 80-909, 103 p.

Reference (Deposit): Fechner, S.A., 1988, Bureau of Mines mineral investigation of the Goodnews Bay mining district, Alaska: U.S. Bureau of Mines Open-File Report 1-88, 230 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Hagemeister Island quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-362, 1 sheet, scale 1:250,000.

Reference (Deposit): Roehm, J.C., 1937, General report of mining and prospecting activities, Goodnews Bay district, Alaska: Alaska Territorial Department of Mines Miscellaneous Report 195-16, 34 p.

Reference (Deposit): Mertie, J.B., Jr., 1940, The Goodnews platinum deposits, Alaska: U.S. Geological Survey Bulletin 918, 97 p.

Reference (Deposit): Mertie, J.B., Jr., 1969, Economic geology of platinum minerals: U.S. Geological Survey Professional Paper 630, 120 p.

Reference (Deposit): Hoare, J.M., and Coonrad, W.L., 1978, Geologic map of the Goodnews and Hagemeister Island quadrangles region, southwestern Alaska: U.S. Geological Survey Open-File Report 78-9-B, two sheets, scale 1:250,000.

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