Alabama-California Mine

Site Name

Primary: Alabama-California Mine
Secondary: American

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Commodity

Primary: Silver
Primary: Gold
Secondary: Lead
Tertiary: Arsenic
Tertiary: Bismuth
Tertiary: Antimony

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Location

State: California
County: Placer
District: Penryn District

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Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.
Administrative Organization: Placer County Planning Department

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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: 1860
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: Bear Mountains Fault Zone

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Alterations

Alteration Type: L
Alteration Text: None reported

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Rocks

Name: Quartz Diorite
Role: Host
Age Type: Host Rock
Age in Years: 139.000000+-
Dating Method: K-Ar
Age Young: Early Cretaceous

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Analytical Data

Not available

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Materials

Ore: Galena
Ore: Argentite
Ore: Gold
Ore: Pyrite
Ore: Telluride
Gangue: Quartz

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Comments

Comment (Deposit): The Alabama and other lode mines in this district are developed in gold-bearing quartz veins emplaced in quartz diorite of the Lower Cretaceous Penryn Pluton. These veins generally strike north, dip steeply, and contain auriferous sulfides as well as native gold (Clark, 1970). Ore at the Alabama-California was oxidized to a depth of at least 200 feet. In general, the main vein at the Alabama-California Mine strikes north, and the dip is nearly vertical. Over a distance of 1,000 feet on the 200-foot level, the vein ranged from 2 to 7 feet in width with 2-4 inches of gouge on each wall. The vein consisted of banded quartz in layers an inch wide with large irregular bunches of oxidized sulfide. At one location, the vein was split into footwall and hanging-wall seams, with the dip flattening to 46 degrees. The best ore at this location was reported to be in layers of quartz on each wall that ranged from two inches to one foot in width. Sulfide content of the vein was about 1%, and there was considerable silver in the ore. Ore minerals included native gold, pyrite, galena, argentite, and telluride. Small amounts of antimony, arsenic, and bismuth were also present. Logan (1927, 1935, 1936) presented information about the nearby Chicago Mine, which was in a geologic setting similar to that of the Alabama Mine.

Comment (Geology): REGIONAL GEOLOGY (continued) 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. 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 south of El Dorado County 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 (Clark and Carlson, 1956).

Comment (Commodity): Commodity Info: In the 1930?s, concentrate reportedly formed about 0.5% of the ore and contained about 9 ounces of gold and 120 ounces of silver per ton.

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

Comment (Commodity): Gangue Materials: Quartz

Comment (Development): Mining of quartz veins in this district began in the 1850?s. Appreciable activity took place at several mines in the 1930? and 1940?s, the most notable of which were the Alabama, Chicago, and Sicily. The Alabama Mine was reopened in 1932 after laying idle since the late 1880?s; it was redeveloped on a quartz claim that was patented in 1894 as the American Mine. During the 1930?s and 1940?s, ore was hoisted in buckets and was processed in a 20-stamp mill. The history of this mine is uncertain subsequent to 1936, but it likely closed during World War II when national restrictions were imposed on the gold-mining industry. It is not known to have been active since the war. Flotation, and likely amalgamation, processes were used at this mine.

Comment (Economic Factors): Clark (1970) estimated production at this mine to be in excess of $1 million.

Comment (Environment): The deposit is in an area of rolling hills, close to a major freeway. It is amidst a semi-developed landscape of large residential parcels. Vegetation is a mixture of grass and oak woodland.

Comment (Geology): LOCAL GEOLOGY The Alabama-California Mine is situated at the western edge of the Sierra Nevada metamorphic belt. Here, Jurassic metamorphosed island-arc volcanic rocks have been intruded by quartz diorite of the Lower Cretaceous Penryn Pluton (Olmsted, 1971; Wagner and others, 1981). The mine is developed along a quartz vein that cuts the plutonic rock. In general, the main vein at the Alabama-California Mine strikes north, and the dip is nearly vertical. Over a distance of 1,000 feet on the 200-foot level, the vein ranged from 2 to 7 feet in width with 2-4 inches of gouge on each wall. At the north end of this level (in 1935), the vein was almost 5 feet wide and consisted of banded quartz in layers an inch wide with large irregular bunches of oxidized sulfide. At the south end of this level, the vein was split into footwall and hanging-wall seams, with the dip flattening to 46o. The best ore at this end was reported in layers of quartz on each wall that ranged from two inches to one foot in width. Sulfide content of the vein was about 1%, and there was considerable silver in the ore. Ore minerals included native gold, pyrite, galena, argentite, and telluride. Small amounts of antimony, arsenic, and bismuth were also present. Ore was oxidized at least down to the 200-foot level.

Comment (Identification): This mine was the most productive of several mines that were resurrected or newly developed in the Penryn Mining District during the 20th century. The district has also been identified as the Stewart?s Flat District. Nearby mines include the Chicago, Elizabeth, and Mary Len, and the Sicily, about a mile to the north.

Comment (Location): Location selected for latitude and longitude is the Alabama Mine shaft symbol on the USGS 7.5-minute Rocklin quadrangle. The mine site is close to Interstate 80.

Comment (Workings): The workings consisted of a standard shaft with ore removed from stopes worked from an unknown number of levels (at least two levels were developed). The shaft was reported to be either 200 or 300 feet deep at minimum. In 1935, drifting along the 200-foot level, followed the vein 565 feet south and 480 feet north of the shaft.

Comment (Geology): REGIONAL GEOLOGY The Alabama-California 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). In the western Placer County-El Dorado County region, gold deposits are present in the West Belt, the Mother Lode Belt, and the East Belt. The Mother Lode Belt is responsible for most of the gold produced. There has also been substantial gold produced from the West Belt and East Belt (Clark and Carlson, 1956). The West Belt of the Sierra Nevada foothills consists of widely scattered gold deposits located west of the Mother Lode vein system, which represents the Mother Lode Belt. The Alabama-California Mine is within this 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. Mesozoic plutonic rocks in this belt are generally of intermediate to mafic composition; the Alabama-California Mine is associated with such rocks. The northwest-trending Mother Lode Belt traverses western El Dorado County and is associated with the Melones Fault Zone. The belt trends north through Nashville, northeast through Placerville, and northwest to Garden Valley. At Garden Valley, the Mother Lode Belt splits. The west branch extends northwest through Greenwood, and the east branch extends north as a continuation of the Melones Fault Zone through Georgetown to the Georgia Slide area. 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.

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References

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.

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

Reference (Deposit): Lindgren, W., 1894, Sacramento Folio: U.S. Geological Survey Atlas of the U.S., Folio 5, 3 p.

Reference (Deposit): Logan, C.A., 1927, Placer County: 23rd Annual Report of the State Mineralogist, California State Mining Bureau, p. 250.

Reference (Deposit): Logan, C.A., 1935, Placer County: 31st Annual Report of the State Mineralogist, California Journal of Mines and Geology, p. 17-18.

Reference (Deposit): Logan, C.A., 1936, Gold mines of Placer County: 32nd Annual Report of the State Mineralogist, California Journal of Mines and Geology, p. 10-11, 16-17.

Reference (Deposit): Olmsted, F.H., 1971, Pre-Cenozoic geology of the south half of the Auburn 15-minute quadrangle, California: U.S. Geological Survey Bulletin 1341, 30 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): Wagner, D.L. and others, 1981, Geologic map of the Sacramento Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 1A, 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): Clark, W.B. and Carlson, D.W., 1956, Mines and mineral resources of El Dorado County: California Division of Mines, California Journal of Mines and Geology, v. 52, p. 408.

Reference (Deposit): Clark, W.B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 103, 105.

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. 40.

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California Gold

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