Red Cloud Mine

Site Name

Primary: Red Cloud Mine
Secondary: Kate Kearney

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Commodity

Primary: Gold
Secondary: Silver

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Location

State: California
County: Mariposa
District: Kinsley District

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Hydrothermal vein
Operation Type: Underground
Discovery Year: 1880
Years of Production:
Organization:
Significant: Y
Deposit Size: S

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Physiography

Not available

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Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

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Orebody

Form: Tabular

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Structure

Type: R
Description: Sonora Fault

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Alterations

Alteration Type: L
Alteration Text: None reported in documents researched

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Rocks

Name: Slate
Role: Host
Age Type: Host Rock
Age Young: Mesozoic
Age Old: Paleozoic

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Pyrite
Gangue: Quartz

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Comments

Comment (Geology): REGIONAL GEOLOGY The Red Cloud Mine is within the Sierra Nevada Mountains, where bedrock consists of northerly trending tectonostratigraphic belts of metamorphosed sedimentary and volcanic rocks and associated intrusive rocks that range in age from Paleozoic to Mesozoic. The structural belts, which extend about 235 miles along the western side of the Sierra, are flanked to the east by the Sierra Nevada Batholith and to the west by sedimentary rocks of the Cretaceous and Jurassic Great Valley sequence. The structural belts are internally bounded by the Melones and Bear Mountains fault zones and are characterized by extensive faulting, shearing, and folding (Earhart, 1988). From El Dorado County southward into Mariposa County, lode gold deposits occur in three distinct belts - the West Belt, the Mother Lode Belt, and the East Belt. The Mother Lode Belt is responsible for most of the gold produced. However, there has also been substantial gold production from the West Belt and East Belt. The West Belt in Mariposa County consists of widely scattered gold deposits located west of the Mother Lode vein system, which represents the Mother Lode Belt. Gold occurs in irregular quartz veins and stringers in schist, slate, granitic rocks, altered mafic rocks, and as gray ore in greenstone. The West Belt is cut by the northwest-trending Bear Mountains Fault Zone, which separates an assemblage of metavolcanic and metasedimentary rocks of Jurassic age on the southwest from a more disrupted and diverse assemblage of metavolcanic, metasedimentary, plutonic, ultramafic, and melange rocks on the northeast. The metavolcanic rocks consist generally of volcanic and volcanic-sedimentary rocks of island-arc affinity. These rocks are mostly mafic to intermediate in composition and include flows, breccias, and a variety of layered pyroclastic rocks. Some silicic rocks are present also. Various formation names assigned to the metavolcanic assemblages include Gopher Ridge, Copper Hill, Logtown Ridge, and Penon Blanco. The metasedimentary rocks are dominantly distal turbidites and hemipelagic sequences of black slate. Assigned formation names include Mariposa, Salt Spring Slate, and Merced Falls Slate. The northwest-trending Mother Lode Belt traverses western Mariposa County and is associated with the Melones Fault Zone. The rocks of this belt are typically metavolcanic, metasedimentary, and ultramafic, some of which have been hydrothermally altered to assemblages as described below. Mother Lode Belt mineralization is characterized by steeply dipping gold-bearing quartz veins and bodies of mineralized country rock adjacent to veins. Mother Lode veins are characteristically enclosed in Mariposa Formation slate with associated greenstone. The Mother Lode belt vein system ranges from a few hundred feet to a mile or more in width. Within the zone are numerous discontinuous or linked veins, which may be parallel, convergent, or en echelon. The veins commonly pinch and swell. Few can be traced more than a few thousand feet. Mother Lode type veins fill voids created within faults and fracture zones and consist of quartz, gold and associated sulfides, ankerite, calcite, chlorite, limonite, talc, chromium-bearing mica, and sericite. Stringer veins are commonly found in both adjacent footwall and hanging walls. Mother Lode ores are generally low- to moderate-grade (1/3 ounce of gold or less per ton), but ore bodies can be large. Ore shoots are generally short, 200-300 feet being the average stope length. However, they persist at depth, some having been mined to several thousand feet (Clark and Lydon, 1962). Ore shoots are commonly localized at bulges in veins, shear zones, vein intersections, or near abrupt changes in strike or dip.

Comment (Geology): Wall rocks have invariably been hydrothermally altered, having been partially to completely converted to ankerite, sericite, quartz, pyrite, arsenopyrite, chlorite, and albite with traces of rutile and leucoxene (Knopf, 1929). The mineralization is generally adjacent to the veins in ground that has been fractured and contains small stringers and lenses of quartz. Locally, greenstone bodies adjacent to the quartz veins contain enough disseminated auriferous pyrite in large enough bodies to constitute what has been called "gray ore.? Altered slate wall rock commonly contains pyrite, arsenopyrite, quartz, chlorite, and sericite with or without ankerite (Zimmerman, 1983). Large bodies of mineralized schist also form low-grade ore bodies throughout the Mother Lode. This ore consists of amphibolite schist that has been subjected to the same processes of alteration, replacement, and deposition that formed the greenstone gray ores. The altered schist consists mainly of ankerite, sericite, chlorite, quartz, and albite. Gold is associated with the pyrite and other sulfides that are present. Pyrite comprises about 8 percent of the rock. The average grade of mineralized schist is about 0.1 oz per ton. The Melones Fault Zone separates the Mother Lode Belt from the East Belt. The East Belt is dominantly argillite, phyllite and phyllonite, chert, and metavolcanic rocks of Paleozoic-Mesozoic age. Carbonate rocks (marble) are also present locally. The phyllite and phyllonite are dark to silvery gray. The chert is mostly thin-bedded with phyllite partings. The Upper Paleozoic-Lower Mesozoic metasedimentary and metavolcanic rocks of the East Belt have been assigned to the Calaveras Complex by most investigators (Earhart, 1988). The Lower Paleozoic metamorphic rocks farther east have been assigned to the Shoo Fly Complex. More recently, some geologists have reinterpreted certain assemblages along and immediately east of the Melones Fault Zone as separate Jurassic units (Schweickert and others, 1999). The metamorphic complexes are intruded in places by Mesozoic plutonic rocks. Lode deposits of the East Belt consist of many individual gold-bearing quartz veins enclosed in metamorphic rocks of possible Jurassic age, metamorphic rocks of the Calaveras Complex, metamorphic rocks of the Shoo Fly Complex, or in granitic rocks. Most of the veins trend northward and dip steeply. An east-west set of intersecting faults may be a controlling factor in controlling deposition of ore. Ore deposits of the East Belt are smaller and narrower than those of the Mother Lode, but commonly are more chemically complex, and richer in grade. Gold is generally associated with appreciable amounts of pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, and arsenopyrite. LOCAL GEOLOGY The Red Cloud Mine is situated in the East Belt of gold mineralization of the Sierra Nevada and is similar in its origin and setting to the nearby Bandarita and Hasloe Mines. The deposit consists of a main gold-bearing quartz vein in slate that is part of the Paleozoic-Mesozoic Calaveras Complex. Regionally, this complex also includes phyllite, metachert, schist, metavolcanic rock, and metacarbonate rock. The vein strikes N40E according to Bowen and Gray (1957); Castello (1921) reported a strike of E-W. It dips 60-80NW, and its width averages 5 feet, with a maximum width of 15 feet. The vein is traceable for a distance of more than 4,500 feet. Vein matter is milky quartz with inclusions of brecciated wall rocks, locally banded or ribboned. Two 3-to-5-foot thick ore shoots, each about 400 feet long, were worked in the upper levels to a depth of over 500 feet. Ore minerals are native gold and auriferous pyrite.

Comment (Identification): The Red Cloud Mine, as discussed here, exploited this gold deposit as a single operation. Various other mining claims are also present in the immediate area.

Comment (Location): Location selected for latitude and longitude is the Red Cloud Mine shaft symbol on the USGS 7.5-minute Buckhorn Peak quadrangle.

Comment (Workings): Principal workings at this mine consist of a 700-foot main inclined shaft with levels at intervals of 100 feet. As of 1957, most of the stoping had been done above the 500-foot level. Drifts aggregated more than 500 feet. As of 1954, the workings were all caved and inaccessible. Metals Economics Group (1983) reported, however, in 1984 that the old workings were in good condition.

Comment (Deposit): The deposit at the Red Cloud Mine consists of a typical gold- and sulfide-bearing hydrothermal quartz vein within metamorphic wall rock. The vein, which is reportedly in slate, strikes either N40E or E-W, according to different reports, and dips 60-80NW. Vein width averages five feet and reaches a maximum of 15 feet. Vein matter is milky quartz with inclusions of brecciated wall rocks, locally banded or ribboned. Two 3-to-5-foot thick ore shoots, each about 400 feet long, were worked in the upper levels to a depth of over 500 feet. Ore minerals are native gold and auriferous pyrite.

Comment (Development): The principal period of operation of the Red Cloud Mine was 1885-1895 when most of the workings were driven and most of the production made. The shaft was deepened to 700 feet in 1893. A 22-stamp mill operated on the property in 1889. Bowen and Gray (1957) were not aware of any active mining on the property between 1935 and 1957. In 1979, Aurum Technologies, Incorporated, of Modesto, California, began exploring the property by means of core drilling, grab sampling, assaying, and a VLF electromagnetic survey. Ore bodies were blocked out with the intention of rehabilitating the mine and bringing it into production by the end of 1984. As of 1988, the mine was still in development, but any subsequent activities at the mine are unknown.

Comment (Commodity): Commodity Info: In the middle 1880?s, ore ran about $30 of gold per ton, mostly native. Average content of sulfides was about 2-1/2 percent. It is not known if there were other sulfides in addition to pyrite.

Comment (Commodity): Ore Materials: Native gold, auriferous sulfides (pyrite)

Comment (Commodity): Gangue Materials: Quartz, brecciated wall rock

Comment (Economic Factors): Castello (1921) stated that the mine was said to have a production record of about $1.5 million, but there are no records to substantiate this estimate. Metals Economics Group (1983) reported that core drilling and assays by Aurum Technologies in 1979-1984 indicated ore bodies contained 1 million short tons of ore averaging 0.5 ounces of gold per ton. Despite this reported tonnage of ore, the size of the deposit is conservatively estimated here to be in the 'small' category.

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References

Reference (Deposit): Julihn, C.E., and Horton, F.W., 1940, Mineral industries survey of the United States - Mines of the southern Mother Lode Region, Part II - Tuolumne and Mariposa counties: U.S. Bureau of Mines Bulletin 424, 179 p.

Reference (Deposit): Castello, W.O., 1921, Mariposa County: California State Mining Bureau, 17th Annual Report of the State Mineralogist, p. 86-143.

Reference (Deposit): Bowen, O.E., Jr. and Gray, C.H., Jr., 1957, Mines and mineral resources of Mariposa County, California: California Journal of Mines and Geology, v. 53, nos. 1-2, p. 35-343.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Division of Mines and Geology Bulletin 193, p. 85.

Reference (Deposit): Clark. W. B., and Lydon, P.A., 1962, Mines and mineral resources of Calaveras County, California: California Division of Mines and Geology County Report No. 2, p. 72-73.

Reference (Deposit): Strand, R.G., 1967, Mariposa Sheet: California Division of Mines and Geology Geologic Map of California, scale 1:250,000.

Reference (Deposit): Wagner, D.L., Bortugno, E.J., and McJunkin, R.D., 1990, Geologic map of the San Francisco-San Jose Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 5A, scale 1:250,000.

Reference (Deposit): Zimmerman, J.E., 1983, The geology and structural evolution of a portion of the Mother Lode Belt, Amador County, California: Unpublished M.S. thesis, University of Arizona, 138 p.

Reference (Deposit): Knopf, A., 1929, The Mother Lode system of California: U. S. Geological Survey Professional Paper 157, 88 p.

Reference (Deposit): Logan, C.A., 1935, Mother Lode gold belt of California: California Division of Mines Bulletin 108, 240 p.

Reference (Deposit): Koschmann, A.H., and Bergendahl, M.H., 1968, Principal gold-producing districts of the United States: U. S. Geological Survey Professional Paper 610, 283 p.

Reference (Deposit): Metals Economics Group, 1983, The MineSearch annual: California, Oregon, and Washington, vol. VIII, 636 p.

Reference (Deposit): Schweickert, R.A., Hanson, R.E., and Girty, G.H., 1999, Accretionary tectonics of the Western Sierra Nevada Metamorphic Belt in Wagner, D.L. and Graham, S.A., editors, Geologic field trips in northern California: California Division of Mines and Geology Special Publication 119, p. 33-79.

Reference (Deposit): Earhart, R.L., 1988, Geologic setting of gold occurrences in the Big Canyon area, El Dorado County, California: U.S. Geological Survey Professional Paper 1576, 13 p.

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