Bandarita Mine

Past Producer in Mariposa county in California, United States with commodities Gold, Silver

Sections on this page

Identification information
Geographic coordinates
Site location context
Geographic areas
Public Land Survey System information
Commodities
Materials information
Alteration
Mineral occurrence model information
Host and associated rocks
Nearby scientific data
Geologic structures
Ore body information
Controls for ore emplacement
Economic information about the deposit and operations
Mining district
Bibliographic references
General comments
Reporter information

Geologic information

Identification information

Deposit ID	10310586
Record type	Site
Current site name	Bandarita Mine
Alternate or previous names	Bandaretta, Eclipse, Goodwin

Comments on the site identification

The Bandarita Mine, as discussed here, exploited this gold deposit as a single operation. Various other mining claims are also present in the immediate area.

Geographic coordinates

Geographic coordinates:	-120.03323, 37.69169 (WGS84)
Location accuracy	100(meters)
Relative position	The Bandarita Mine is about 9 miles east-southeast of the town of Coulterville.

Site location context

Political divisions (FIPS codes)

Mariposa(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Buckhorn Peak(quadrangle 1:24,000 scale)

Oakdale(quadrangle 1:100,000 scale)

San Jose(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Upper Merced(hydrologic unit)

San Joaquin(hydrologic accounting unit)

San Joaquin(hydrologic subregion)

California(hydrologic region)

Federal lands

Stanislaus National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country	State	County
United States	California	Mariposa

Public Land Survey System information

Meridian	Township	Range	Section	Fraction	State
Mount Diablo	003S	018E	07	NW	California

Comments on the location information

Location selected for latitude and longitude is the Bandarita Mine adit symbol (west side of river) on the USGS 7.5-minute Buckhorn Peak quadrangle.

Commodities

Commodity	Importance
Gold	Primary
Silver	Secondary

Comments on the commodity information

Commodity Info: the Goodwin ore shoot reportedly averaged 0.57 ounces of gold per ton. Bowen and Gray (1957) reported that in 1874 a single mill cleanup yielded 25 pounds of gold from 100 tons of ore. Ore that averaged $25/ton was obtained from at least one location in the main crosscut working.
Ore Materials: Native gold, auriferous sulfides (pyrite, galena, sphalerite, tetrahedrite, and arsenopyrite).
Gangue Materials: Quartz, fault gouge

Materials information

Materials	Type of material
Gold	Ore
Pyrite	Ore
Galena	Ore
Sphalerite	Ore
Tetrahedrite	Ore
Arsenopyrite	Ore
Quartz	Gangue

Alteration

(Local) None reported except for vague references by Thompson (1934) to alteration of the dikes.

Mineral occurrence model information

Model code	273
USGS model code	36a
Deposit model name	Low-sulfide Au-quartz vein
Mark3 model number	27

Host and associated rocks

Host or associated

Host

Rock type

Metamorphic Rock > Metasedimentary Rock > Slate

Rock unit name

Calaveras Complex

Stratigraphic age (youngest)	Mesozoic
Stratigraphic age (oldest)	Paleozoic

Host or associated

Host

Rock type

Metamorphic Rock > Hornfels

Rock type qualifier

quartz-biotite

Stratigraphic age (youngest)	Mesozoic
Stratigraphic age (oldest)	Paleozoic

Host or associated Host

Rock type Plutonic Rock > Granitoid > Granodiorite

Stratigraphic age (youngest) Mesozoic

Nearby scientific data

(1)	-120.03323, 37.69169	ListMap

Economic information

Geologic structures

Type of structure	Regional
Structure description	Sonora Fault

Ore body information

General form Tabular

General form	Tabular

Controls for ore emplacement

Ore shoots within quartz veins

Comments on the geologic information

REGIONAL GEOLOGY

The Bandarita 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.
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 Bandarita Mine is situated in the East Belt of gold mineralization of the Sierra Nevada. 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. Other reported rocks associated with the deposit include quartz-biotite hornfels and granodiorite. The granodiorite is present as four individual north-trending dikes that intersect the vein at approximately right angles. Thompson (1934) observed that some of the dikes were altered and leached. The vein strikes N84W and dips 47SW. Its width varies from 2 to 10 feet. Ore consists of quartz with native gold, pyrite, galena, sphalerite, arsenopyrite, and tetrahedrite. The best ore contained considerable tetrahedrite. Thompson (1934) concluded that this ore formed on fault planes that exhibited much movement, which produced a quartz-slate gouge in places. He reported the presence of native gold in the gouge as well as in some of the altered dikes.

Economic information about the deposit and operations

Operation type	Underground
Development status	Past Producer
Commodity type	Metallic
Deposit size	Small
Significant	Yes
Discovery year	1856

Mining district

District name	Kinsley District

Comments on the workings information

Workings at this mine consist of adits, crosscuts, drifts, and stopes, some of which are daylighted. The mine is developed by a 1,364-foot crosscut adit and by six adits driven along the strike of the vein. The crosscut adit intersects the vein about 850 feet vertically from the surface. Stoping along three ore shoots in one adit ranged from 75 to 650 feet to the surface. Thompson (1934) estimated at least 5,000 feet of workings.

Comments on other economic factors

Clark (1970) reported a production value of $1.52 million for this mine. In 1940, it was reported that there were still 275,000 tons of gob remaining in the old stopes.

Comments on development

Opened in 1856, this mine was worked almost continuously until 1887 and then sporadically afterward. Its most productive period was 1881-1887. It was last known to be operated from 1937 to 1943 when $40,000 in gold and silver were obtained from 7,362 tons of ore mined from the Goodwin ore shoot.

Amalgamation processes were used at this mine.

Reference information

Bibliographic references

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.
Deposit

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

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

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

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

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

Thompson, G.L., 1934, Report on the property of Bandarita Consolidated Gold Mining Company, North Fork of Merced River, Mariposa County, California: Unpublished consulting report, 12 p.
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.

General comments

Subject category	Comment text
Deposit	The deposit at the Bandarita Mine consists of a typical gold- and sulfide-bearing hydrothermal quartz vein within metamorphic wall rock. The vein is reportedly in slate, quartz-biotite hornsfels, and granodiorite. The granodiorite is present as four individual north-trending dikes that intersect the vein at approximately right angles. The vein strikes S84W, dips 47SE, and ranges in thickness from 2 to 10 feet. Gold is present both in native form and in sulfides; the gold content was reportedly roughly proportional to the quantity of tetrahedrite present. Thompson (1934) concluded that the ore is present on fault planes along which much movement has taken place. Here, the quartz and slate have been crushed to a gouge.

Subject category

Comment text

Deposit

The deposit at the Bandarita Mine consists of a typical gold- and sulfide-bearing hydrothermal quartz vein within metamorphic wall rock. The vein is reportedly in slate, quartz-biotite hornsfels, and granodiorite. The granodiorite is present as four individual north-trending dikes that intersect the vein at approximately right angles. The vein strikes S84W, dips 47SE, and ranges in thickness from 2 to 10 feet. Gold is present both in native form and in sulfides; the gold content was reportedly roughly proportional to the quantity of tetrahedrite present. Thompson (1934) concluded that the ore is present on fault planes along which much movement has taken place. Here, the quartz and slate have been crushed to a gouge.

Reporter information

Type	Date	Name	Affiliation	Comment
Reporter	10-OCT-2006	Higgins, Chris T.	California Geological Survey CGS (Formerly CDMG)
Editor	01-SEP-2007	Schruben, Paul G.	U.S. Geological Survey	Converted from S&A FileMaker format to Oracle. Edit checks on rocks, units, and ages with Geolex search, and other fields.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

External references

Wikidata: Q49398396 (Bandarita Mine)

Maps centered on this site

Authoritative California resources

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