Demarest Mine, Fourth Crossing, San Andreas Mining District, Calaveras County, California, USAi
| Regional Level Types | |
|---|---|
| Demarest Mine | Mine |
| Fourth Crossing | Unincorporated Community |
| San Andreas Mining District | Mining District |
| Calaveras County | County |
| California | State |
| USA | Country |
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Latitude & Longitude (WGS84):
38° 7' 0'' North , 120° 39' 5'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| San Andreas | 2,783 (2011) | 9.2km |
| Angels Camp | 2,677 (2012) | 11.2km |
| Copperopolis | 3,671 (2011) | 15.1km |
| Mountain Ranch | 1,628 (2011) | 15.7km |
| Vallecito | 442 (2011) | 15.8km |
Nearest Clubs:
Local clubs are the best way to get access to collecting localities
Local clubs are the best way to get access to collecting localities
| Club | Location | Distance |
|---|---|---|
| Calaveras Gem & Mineral Society | Angels Camp, California | 11km |
| Amador County Gem & Mineral Society | Sutter Creek, California | 33km |
A former lode Au mine located in the NE¼ sec. 16, T3N, R12E, MDM, 2.2 km (1.4 miles) SW of Fourth Crossing, on the divide between the South Fork Calaveras River and San Domingo Creek (7 miles SE of San Andreas). Originally operated in the 1850's and in the 1860's, 1897 to 1901, 1904, 1924 to 1937 and 1938 to 1939. MRDS database stated accuracy for this location is 100 meters.
Mineralization is hosted in rocks of the Calaveras Complex, Mariposa Formation and the Leona Rhyolite (slate, phyllite). The ore body is a pinch & swell body, strikes NW and dips NE at a thickness of 3.05 meters. There are 3 veins but only the middle vein, which is 6 to 10 feet thick, was worked. A small amount of country rock is green schist. Gouge on the hanging wall of the vein on the N side of the shaft, but the same distance S of the shaft flecking of veuin & gouge passes to the footwall side. Dikes of medium-grained diorite are also present. The middle vein is on a contact strip of Mariposa slate, 150 feet wide to the W and Calaveras Formation the same 200 foot wide to the E. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).
Workings include underground openings with an overall depth of 182.88 meters, and comprised of a 690 foot, 60 degree inclined shaft with levels at 100, 300, 400 and 600 feet. Drifts from 300 to 420 feet, all driven S from the shaft. The ore shoot S of the shaft had an average stope length of 225 feet with an hour glass shape when viewed laterally, with the narrowest portion at the 500 foot level.
Production data are found in: Clark, Wm. B. & P.A. Lydon (1962).
$40,000 (period values) came from the stope from the 400 level to within 80 feet of surface.
No production record found.
Analytical test results: Approximately $9 (period values) of Au per ton (1934).
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsDetailed Mineral List:
| ⓘ Native Gold Formula: Au |
| ⓘ Quartz Formula: SiO2 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 1 - Elements | |||
|---|---|---|---|
| ⓘ | Native Gold | 1.AA.05 | Au |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Quartz | 4.DA.05 | SiO2 |
List of minerals for each chemical element
| O | Oxygen | |
|---|---|---|
| O | ⓘ Quartz | SiO2 |
| Si | Silicon | |
| Si | ⓘ Quartz | SiO2 |
| Au | Gold | |
| Au | ⓘ Native Gold | Au |
Other Databases
| Link to USGS MRDS: | 10102653 |
|---|
Other Regions, Features and Areas containing this locality
North AmericaContinent
North America PlateTectonic Plate
- Calaveras-Baker DomainDomain
- Sierra Nevada BatholithVolcanic Arc
USA
- California
- Mother Lode BeltBelt
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References
(n.d.) Minerals Availability System (MAS), U.S. Bureau of Mines.file ID #0060090335
