Thorn Mine (Illinois Mine), Fourth Crossing, San Andreas Mining District, Calaveras County, California, USAi
| Regional Level Types | |
|---|---|
| Thorn Mine (Illinois Mine) | Mine |
| Fourth Crossing | Unincorporated Community |
| San Andreas Mining District | Mining District |
| Calaveras County | County |
| California | State |
| USA | Country |
This page is currently not sponsored. Click here to sponsor this page.
Latitude & Longitude (WGS84):
38° 7' 1'' North , 120° 39' 29'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| San Andreas | 2,783 (2011) | 9.0km |
| Angels Camp | 2,677 (2012) | 11.7km |
| Copperopolis | 3,671 (2011) | 15.2km |
| Mountain Ranch | 1,628 (2011) | 16.1km |
| Vallecito | 442 (2011) | 16.4km |
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 | 12km |
| Amador County Gem & Mineral Society | Sutter Creek, California | 33km |
A former lode Au occurrence/mine located in the N½ sec. 16, T3N, R12E, MDM, 2.6 km (1.6 miles) SW of Fourth Crossing, S of Steele Creek and S of the South Fork Calaveras River, in its headwaters area (5½ miles S of San Andreas on Copperopolis Road; N of the Demarest Mine). MRDS database stated accuracy for this location is 500 meters.
Mineralization is a vein deposit hosted in slate, schist and serpentinite. There are 2 veins, one of "ribbon rock," and one of "gray ore." One vein strikes NO5E, the other N30W and converge going N. The footwall is slate and the hanging wall is schist, also with a serpentine dike. They lie W of a greenstone occurrence. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) and/or Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains).
Workings include underground openings comprised of a 200 foot inclined shaft with 2 levels.
Production data are found in: Clark, Wm. B. & P.A. Lydon (1962).
No other production record was found.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsDetailed Mineral List:
| ⓘ Gold Formula: Au |
| ⓘ Quartz Formula: SiO2 |
| ⓘ 'Serpentine Subgroup' Formula: D3[Si2O5](OH)4 Description: Occurs as a dike. |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 1 - Elements | |||
|---|---|---|---|
| ⓘ | Gold | 1.AA.05 | Au |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| Unclassified | |||
| ⓘ | 'Serpentine Subgroup' | - | D3[Si2O5](OH)4 |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| O | Oxygen | |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| Si | Silicon | |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| Au | Gold | |
| Au | ⓘ Gold | Au |
Other Databases
| Link to USGS MRDS: | 10028834 |
|---|
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
This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to
visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders
for access and that you are aware of all safety precautions necessary.
