Tomboy & Eureka Mine (Tomboy and Eureka), Old Mountain House, Alleghany Mining District (Forest Mining District), Sierra County, California, USAi
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Latitude & Longitude (WGS84):
39° 29' 10'' North , 120° 52' 45'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Downieville | 282 (2011) | 9.3km |
| Pike | 134 (2011) | 11.5km |
| Camptonville | 158 (2011) | 15.0km |
| Washington | 185 (2011) | 15.7km |
| Sierra City | 221 (2011) | 22.8km |
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 |
|---|---|---|
| Nevada County Gem & Mineral Society | Grass Valley, California | 34km |
A former lode Au occurrence/mine located in sec. 29, T19N, R10E, MDM, 1.9 km (1.2 miles) SE of Old Mountain House and 2.3 km (1.4 miles) WSW of Forest, along the N side of Mountain House Road, N of Oregon Creek (2 ¼ miles NW of Alleghany), on National Forest land. MRDS database stated accuracy for this location is 100 meters. Adjoins the Kate Hardy Mine.
Mineralization is a vein deposit hosted in serpentinite, gabbro and granite. The ore body strikes NE and dips 67SE. The Tomboy vein is quartz and porphyry with gabbro walls, averages 6 to 7 feet thick and strikes NE, dipping 60-75S, with abundant sulfides. The Eureka vein is 3 to 5 feet thick, strikes NE, and dips flat to E, with the ore in quartz lenses. Both veins exhibit post-mineraliztion shearing. A dike of granite 3 feet thick cuts gabbro and is cut by shear zones accompanying the vein (in the lower Eureka tunnel). Post-mineralization shearing has left quartz of the Eureka vein much crushed, irregular, and in places, absent. Carbonate alteration of the wall rock is not priominent except close to the vein. Local rocks include Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range).
Workings include surface and underground openings comprised of 2 adits, 1 shaft at the Tomboy plus several shafts & adits at the Eureka, plus surface cuts.
Production data are found in: MacBoyle, Errol (1920b).
No other production record was found.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsGallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 1 - Elements | |||
|---|---|---|---|
| ⓘ | Gold | 1.AA.05 | Au |
| Group 2 - Sulphides and Sulfosalts | |||
| ⓘ | Pyrite | 2.EB.05a | FeS2 |
| 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 |
| S | Sulfur | |
| S | ⓘ Pyrite | FeS2 |
| Fe | Iron | |
| Fe | ⓘ Pyrite | FeS2 |
| Au | Gold | |
| Au | ⓘ Gold | Au |
Other Databases
| Link to USGS MRDS: | 10086528 |
|---|
Other Regions, Features and Areas containing this locality
North AmericaContinent
North America PlateTectonic Plate
- Calaveras-Baker DomainDomain
- Sierra Nevada BatholithVolcanic Arc
USA
- Sierra NevadaMountain Range
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References
(n.d.) Minerals Availability System (MAS), U.S. Bureau of Mines.file #0060910238
