Gold Bank Mine

Site Name

Primary: Gold Bank Mine
Secondary: Forbestown Consolidated Gold Mines

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Commodity

Primary: Gold
Secondary: Silver

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Location

State: California
County: Butte
District: Forbestown 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: 1887
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

Not available

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Alterations

Not available

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Rocks

Name: Syenite
Role: Host
Age Type: Host Rock
Age Young: Mesozoic

Name: Diorite
Role: Host
Age Type: Host Rock
Age Young: Mesozoic

Name: Amphibole Schist
Role: Host
Age Type: Host Rock
Age Young: Mesozoic

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Pyrite
Gangue: Quartz
Gangue: Telluride

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Comments

Comment (Identification): This mine later became the main property holding in the Forbestown Consolidated Gold Mines. This group also included the Golden Queen, Golden King, Shakespeare, and Miller mines, among others. Logan (1930) considered the group to probably be the most important lode property in the county.

Comment (Location): Location selected for latitude and longitude is the Gold Bank adit symbol on the USGS 7.5-minute Forbestown quadrangle.

Comment (Deposit): This deposit is typical of others in the Sierra Nevada foothills in that gold and silver mineralization is found in quartz veins and low concentrations of disseminated sulfides. The main vein exploited at the Gold Bank Mine is east-west-trending, dips moderately to the north, and averages about six feet in width. It contains native gold, silver, and 2-7% sulfides, which are dominantly pyrite with some copper sulfides. Telluride minerals may also be present. Elsewhere in the Forbestown District, some mineralization at the Shakespeare Mine is present in the form of quartz stringers; galena is also present here.

Comment (Workings): Early operations consisted of multiple adits and an inclined shaft on the main vein. Logan (1930) reported the largest stope to be about 450 feet along strike and 600 feet along dip. The stope width observed at one location ranged from 3 to 11 feet.

Comment (Development): The Gold Bank Mine was worked prior to 1887. Principal mining activity took place from 1888 to 1904. At its height of production, a 60-stamp mill was in operation. Logan (1930) reported the last work done on the Gold Bank was in 1916. Chlorination and amalgamation were used at this mine. An exploratory project was conducted at this mine in the 1980?s.

Comment (Economic Factors): Total output of the Gold Bank Mine to 1930 was estimated at about $2 million.

Comment (Geology): REGIONAL GEOLOGY The Gold Bank Mine is situated within the westernmost part of the Sierra Nevada geologic province. This province is characterized by extremely complex lithologies and structures that were assembled through various plate-tectonic processes. Paleozoic-Mesozoic metamorphic complexes intruded by various Mesozoic plutons compose the basement of the province. This basement is overlain at higher elevations by erosional remnants of Cenozoic volcanic and sedimentary rocks, including gravels. Most of these various lithologies contain gold in places. Structurally, the metamorphic rocks and some of the plutonic rocks have been deformed by folding and faulting. The major fault zones typically trend northerly or northwesterly, although in places intrusion of the younger plutons has deformed some of the zones so as to assume other trends as well. In contrast, the overlying Cenozoic rocks are relatively undeformed. LOCAL GEOLOGY The mine is situated in a unit mapped by Saucedo and Wagner (1992) as metavolcanic rock of the Jurassic Smartville Complex. Logan (1930) described the country rock as amphibolite schist. To the north is intermediate-composition plutonic rock of the Mesozoic Bald Rock Pluton and to the south is gabbroic rock of the Smartville Complex. The main vein strikes approximately east and has an average dip of 35o north. Its width averages about six feet. The hanging wall reportedly is diorite, while the footwall reportedly is syenite. The ore is solid white quartz with subordinate ribbon structures near the walls. It formed as lenses on both walls. Gold is present in native form and in sulfides (primarily pyrite with some unspecified copper sulfide). Silver is also present, and there is some evidence of tellurides.

Comment (Commodity): Commodity Info: the sulfides were erratically distributed in bunches and formed 2-7 percent of the ore. Gold and silver are present in the sulfides.

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

Comment (Commodity): Gangue Materials: Quartz, tellurides

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References

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Division of Mines and Geology Bulletin 193, p. 48-49.

Reference (Deposit): Logan, C.A., 1930, Butte County: California State Mining Bureau, 26th Report of the State Mineralogist, p. 373-376.

Reference (Deposit): Miner, J.A., 1890, Gold Bank Mine: California State Mining Bureau, 10th Report of the State Mineralogist, p. 125-127.

Reference (Deposit): Saucedo, G.J. and Wagner, D.L., 1992, Geologic map of the Chico Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 7A, scale 1:250,000.

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California Gold

"Where to Find Gold in California" looks at the density of modern placer mining claims along with historical gold mining locations and mining district descriptions to determine areas of high gold discovery potential in California. Read more: Where to Find Gold in California.