Angels Camp Mining District, Calaveras County, California, USAi

Regional Level Types
Angels Camp Mining District	Mining District
Calaveras County	County
California	State
USA	Country

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Location
This district is in southwest Calaveras County in the vicinity of the town of Angels Camp and Altaville. It is an important part of the Mother Lode belt and lies between the San Andreas district to the northwest and the Carson Hill district to the southeast. It is both a lode and placer district, but the lode mines have been more productive.

History
The streams in the area were mined shortly after the beginning of the gold rush. The town was founded in 1848 and named for Henry Angel, who had established a trading post here. Rich surface ores were mined in the oxidized zones in the 1850s, and most of the important veins were discovered at that time. By 1885 Angels Camp had become one of the major gold-mining districts in the state. The Utica Mining Company was organized in the middle 1850s, and for the next 40 years the Utica mine was a major source of gold. From 1893 to 1895 this mine yielded more than $4 million worth of gold. All of the major mines were shut down during World War I. There was some activity in the district again during the 1930's, and the Calaveras Central and Altaville drift mines have been intermittently prospected during the past 15 years. This district has an estimated total output of at least $30 million, and it may be considerably more. The colorful jumping frog jubilee held each year at nearby Frogtown, the county fairgrounds, is based on Mark Twain's tale, The Jumping Frog of Calaveras County. He is supposed to have first related the story at the Angels Hotel.

Geology
This district is underlain by a series of northwest-striking beds of amphibolite and chlorite schist, phyllite, greenstone, and metagabbro. To the east and west are slate, impure quartzite, and micaceous schist. In the north and northeast part of the district is the west and northwest-trending Tertiary Central channel, which is a tributary of the ancestral Calaveras River. The channel gravels are cemented, contain abundant quartz, and are overlain by rhyolite tuff and andesite.

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).
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.

Ore Deposits
The lode deposits consist of massive quartz veins, zones of parallel quartz stringers and bodies of mineralized schist and greenstone. The ore contains disseminated free gold and auriferous pyrite. Usually the gold is in fine particles, although occasional high-grade pockets containing coarse gold have been found. Calcite, talc, ankerite, and sericite, are commonly present in the ore. The milling-grade ore usually averaged 1/7 to 1/5 ounce of gold per ton, but the ore bodies were scores of feet in thickness, hundreds of feet in length, and were mined to depths of several thousand feet.

The deposits occur either in the amphibolite and chlorite schist or phyllite. There are three principal vein systems. In the system on the west the veins are in phyllite. In the center one the veins are along the west margin of a northwest-trending belt of metagabbro. In the eastern system, which contains the famous Utica mine, the ore deposits are in amphibolite and greenstone.

Mines
Lode: Altaville, Angels $3.25 million+, Angels Deep $100,000+, Belmont-Osborn $100,000+, Benson, Big Spring, Bruner, Bullion, Chaparral Hill, Cherokee, Evening Star, Ghost, Gold Cliff $2,834,- 000+, Gold Hill $100,000+, Great Western, Hardy, Keystone, Last Chance, Lightner $3 million+, Lindsey, Madison $1 million+, Marble Springs, Mohawk, Mother Lode Central $100,000+, Oriole, Parnell, Pure Quill, Santa Ana, Sultana $200,000+, Tollgate, Triple Lode, Tulloch, Utica $17 million, Vonich, Whittle, Wagon Rut, Waterman, Yellowstone. Drift: Altaville, Calaveras Central 22,000 ounces+.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.

Mineral List

Mineral list contains entries from the region specified including sub-localities

20 valid minerals.

Rock Types Recorded

Rock list contains entries from the region specified including sub-localities