Lightner Mine

Site Name

Primary: Lightner Mine

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Commodity

Primary: Gold
Secondary: Silver

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Location

State: California
County: Calaveras
District: Angels Camp

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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: City of Angels Camp

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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: 1850
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, pinch and swell

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Structure

Type: L
Description: Melones Fault Zone

Type: R
Description: Bear Mountains fault zone, Melones fault zone

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Alterations

Alteration Type: L
Alteration Text: Ankeritic and sericitic alteration of wall rock with disseminated aurtiferous pyrite mineralization

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Rocks

Name: Schist
Role: Host
Description: chloritic and talcose
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: Calcite
Gangue: Talc
Gangue: Chalcopyrite
Gangue: Ankerite
Gangue: Sericite

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Comments

Comment (Location): Location selected for latitude and longitude is the Lightner Mine shaft symbol on the USGS 7.5 minute Angels Camp quadrangle

Comment (Workings): The Lightner Mine was developed by a 1050-foot, 3-compartment, vertical shaft. Levels were turned at 200, 300, 400, 500, 600, and 900 feet with drifts on all levels to the claim lines except on the 900 foot level which was driven only 40 feet to the south, for a total of 2150 feet of drifts. From the 600-foot level a winze was sunk to the 900-foot level and a crosscut run to cut the ore body below the talc zone. There was also a cross-cut 150 feet from the shaft on the 900-foot level (Logan, 1934). The mine was substantially timbered with a modification of the square-set system. Ore was hoisted in 3-ton skips by a double-drum electric hoist and dumped over a grizzly before crushing in a 10" x 20" Blake crusher. There was a 500-ton storage bin under the crusher. The mine had a 40-stamp electric mill. Storms (1900) provides a good description of the milling operations at the turn of the century. The mill was later upgraded to 60 stamps. Battery pulp was concentrated on thirty-six 4-foot Frue vanners (Tucker, 1916; Clark and Lydon, 1962). One-half of the gold values were recovered by amalgamation inside the batteries, one-fourth on outside plates, and one-fourth by concentration. Recovery was 90% (Tucker, 1916).

Comment (Deposit): The Lightner Mine produced over $3 million from ore bodies consisting of numerous lenticular quartz-calcite stringer veins separated by various thicknesses of fissured mineralized amphibolite and chloritic and talcose schist. The stringers strike about N 50? W and dip steeply to the northeast, lying nearly in the planes of schistosity of the country rock. Both the quartz stringers and country rock contain free gold and auriferous pyrite, although most of the gold occurs within the mineralized schist. The grade of ore varied greatly. Ore grades reported for the adjoining Utica Mine which developed the same ore body yielded as much as $13.02 per ton but declined to $3.60 or less per ton with depth. Ore averaged about 2% concentrates yielding about $40 to $70 per ton.

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 usually 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 Eastern Belt is dominantly argillite, phyllite and phyllonite, chert, and metavolcanic rocks of Paleozoic-Mesozoic age. The phyllite and phyllonite are dark to silvery gray. The chert is mostly thin bedded with phyllite partings. The Paleozoic-Mesozoic metasedimentary and metavolcanic rocks of the Eastern Belt have been assigned to the Calaveras Complex by most investigators (Earhart, 1988). Older Paleozoic metamorphic rocks have been assigned to the Shoo Fly Complex. The metamorphic complexes have 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 usually associated with appreciable amounts of pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, and arsenopyrite. LOCAL GEOLOGY The geology of the Angels Camp district is complex. Bedrock, which is assigned either to the Calaveras Complex or unnamed units of Jurassic age, consists of a series of northwest-striking beds of amphibolite and chlorite schists, phyllite, greenstone, and metagabbro. Ore deposits occur either in amphibolite and chlorite schist or phyllite. There are three principal northwest striking vein systems in the district. In the westernmost system, the veins are in phyllite. In the center system, the veins are along the western margin of a northwest trending belt of metagabbro. In the eastern system, which includes the Lightner Mine, the ore deposits occur in amphibolite and greenstone. To the east and west of the district, bedrock is composed of slate, impure quartzite, and micaceous schist (Clark, 1970).

Comment (Geology): The low-grade ore bodies in the Lightner and adjoining Utica mine are not within simple gold-quartz veins like many Mother Lode deposits, but instead consist of numerous lenticular quartz-calcite stringer veins separated by various thicknesses of mineralized fissured amphibolite and chloritic and talcose schist. Nonetheless, the mineralized zone was designated the Utica vein (or Bonanza vein) in mine records. Geologically, the Lightner Mine is an extension of the ore body developed in the larger neighboring Utica Mine. In the Lightner Mine, the Utica vein ranged from 10 to 120 feet thick (Storms, 1900; Clark and Lydon, 1962). Specific information regarding the nature of the ore in the Lightner Mine is meager. However, several records cite its similarity to ore in the adjoining Utica Mine for which there is considerably more information, and from which this description is largely drawn. The stringers range from a few inches to three feet thick and are largely quartz, but carbonate is abundant, especially in the smaller fissures. The stringers strike about N 50? W and dip steeply northeast to vertical, lying nearly in the planes of schistosity of the country rock (Eisenhauer, 1932). Both the quartz and nearby country rock contain free gold and auriferous pyrite. The schist is greatly altered and pyritized and carries the greater gold values. The schists are largely altered and compose of ankerite and sericite, with subordinate quartz, albite, and pyrite. The richest ore was called "brown quartz", consisting of a fine granular aggregate of quartz, dolomite, and sometimes albite, with abundant small crystals of pyrite. The brown quartz does not always form well-defined veins or stringers, but is intimately associated with the country rock, and is in part an altered form of the country rock. The other vein minerals are free gold, sericite, and chalcopyrite. Gold is not visible in most of the ore, but occurs in considerable masses in certain rich streaks (Ransome, 1900). The rich brown quartz ore was confined to the shallow workings above the 600-foot level and where the ore body was 120 feet wide. Between the 500 and 600-foot levels the ore body was cut off by a zone of talc 15 to 20 feet thick with a dip of 30? NE (Tucker, 1916). This truncation and a similar talc zone were encountered within the Utica vein in the adjoining Utica Mine where Eisenhauer (1932) and McCurdy (1932) interpreted the abrupt flooring of the ore body to a reverse fault plane within the talc zone, above which the best ore occurred in the hanging wall. The ore body is said to have been picked up below the talc zone in a crosscut run 150 feet on the 900-foot level, but its dip had steepened to between 80?E and vertical (from 65?-71? above the talc) and the ore body had split into three distinctive vein zones, separated by barren schist about 100 feet north of the shaft (Clark and Lydon, 1962). The grade of ore varied greatly. Information about the ore body in the Utica Mine indicates the shallowest ores yielded as much as $13.02 per ton but declined to $3.60 or less with depth. Occasionally small high-grade pockets were found. Pyrite and chalcopyrite are the only sulfides reported in the ore. Ore averaged about 2% concentrates.

Comment (Development): The Lightner Mine was originally worked prior to 1857. By 1860, the mine was opened by a 70-foot open cut and equipped with a 10-stamp mill, but the venture proved uneconomic. The mine was idle until 1896, when it was reopened by the newly incorporated Lightner Gold Mining Company with a capitalization of $125,000. By 1897, it was only 200 feet deep, but in 1898 it was being actively developed with new machinery and sufficient ore was being produced to run a new 40-stamp mill. Except for 1910, during which the mine was shut down due to a caving of the shaft, the mine was continuously active until 1915 when it was shut down (Clark and Lydon, 1962). From 1896 until 1915, approximately 500,000 tons of ore were mined which yielded more than $3 million. Ultimately, the Lightner Gold Mining Company paid $550,000 in dividends, and when the property was closed the company claimed the mine still contained 200,000 tons of ore above the 300-foot level (Logan, 1934). The mine was dewatered in 1920, but there was no production and it has been idle ever since (Clark and Lydon, 1962).

Comment (Economic Factors): The Lightner Mine is thought to have produced about $3+ million (Clark, 1970).

Comment (Geology): REGIONAL GEOLOGY The Angels Camp district is within the Sierra foothills, where bedrock consists of north trending tectonostratigraphic belts of metamorphosed sedimentary, volcanic, and intrusive rocks that range in age from late 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 Tuolumne County, lode gold deposits occur in three distinct lithologic belts - the West Gold Belt, the Mother Lode Belt, and the East Gold 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 consists of widely scattered gold deposits located west of the Mother Lode vein system. 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 can be divided into an eastern component composed of an ophiolitic melange and a western component composed of Jurassic rocks of the Copper Hill volcanics, Salt Springs slate, and Gopher Ridge volcanics. The Bear Mountains fault zone separates the melange from the Copper Hill volcanics. The Mother Lode Belt traverses western Calaveras County and consists of the upper Jurassic Logtown Ridge and upper Jurassic Mariposa formations. The Logtown Ridge Formation consists of about 6,500 feet of volcanic and volcanic-sedimentary rocks of island arc affinity. These rocks are mostly basaltic and include flows, breccias, and a variety of layered pyroclastic rocks. The overlying Mariposa Formation contains a distal turbidite, hemipelagic sequence of black slate, schist, amphibolite and chlorite schist, fine-grained tuffaceous rocks, and subvolcanic intrusive rocks. The thickness of the Mariposa Formation is difficult to ascertain due to structural complexities, but is estimated to be about 2,600 feet thick at the Cosumnes River (Earhart, 1988). Mother Lode 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, 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 (Identification): The Lightner Mine is located within the city of Angels Camp in southwestern Calaveras County, California. The gold mines in and around Angels Camp are part of the Angels Camp mining district, which is credited with producing at least $30 million in gold (Clark, 1970). The Lightner Mine reportedly produced in excess of $3 million and lies between the Angels Mine ($3.25 million) to the north and the Utica Mine ($17 million), which it adjoins, to the south. The Lightner Mine was originally worked on a small scale as an open cut prior to 1857, but lay idle from 1860 until 1896 when the Lightner Gold Mining Company was founded. Except for 1910, during which the mine was shut down due to a caving of the shaft, the mine was continuously active until 1915 when it was shut down. During this period, approximately 500,000 tons of ore were mined which yielded more than $3 million.

Comment (Commodity): Ore Materials: Quartz-calcite stringer veins containing free gold and auriferous pyrite, and mineralized schist wallrock

Comment (Commodity): Gangue Materials: Quartz, calcite, talc, chalcopyrite, ankerite, and sericite

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References

Reference (Deposit): Clark, L.D., 1970, Geology of the San Andreas 15-minute quadrangle, Calaveras County, California: California Division of Mines and Geology Bulletin 195, 23 p.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 25-28.

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. 60-61.

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): Eric, J.H., Stromquist, A.A., and Swinney, C.M., 1955, Geology and mineral deposits of the Angels Camp and Sonora quadrangles, Calaveras and Tuolumne counties, California: California Division of Mines Special Report 41, 55 p.

Reference (Deposit): Logan, C. A., 1934, Mother Lode Gold belt of California: California Division of Mines and Geology Bulletin 108, p. 140-141.

Reference (Deposit): Storms, W.H., 1900, The Mother Lode region - Calaveras County: California State Mining Bureau Bulletin 18, p 109-111.

Reference (Deposit): Tucker, W.B., 1916, Calaveras County, Lightner Mine: California State Mining Bureau, 14th Annual Report of the State Mineralogist, p. 89-90.

Reference (Deposit): Eisenhauer, R. C., 1932, Preliminary report on the property of the Utica Mining Company: unpublished geological report for the Utica Mining Company.

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.

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California Gold

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