Bunker Mine (Bunker Mines; Blue Bird Mine [1880's]; Bay Tree prospect; Sunnyside occurrence), Sage Hill, Michigan Bluff Mining District (Michigan Bluff Mining deposit), Placer County, California, USAi
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Latitude & Longitude (WGS84):
39° 2' 13'' North , 120° 45' 34'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Foresthill | 1,483 (2011) | 5.4km |
| Georgetown | 2,367 (2011) | 16.0km |
| Colfax | 2,005 (2017) | 18.2km |
| Alta | 610 (2011) | 19.4km |
| Dutch Flat | 160 (2011) | 20.0km |
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 | 33km |
| El Dorado County Mineral and Gem Society | Placerville, California | 34km |
| Gold Country Treasure Seekers | Placerville, California | 34km |
A former Cr-Fe occurrence/mine located in the S½SE¼ and in the SE¼SW¼ sec. 20, T14N, R11E, MDM, 0.6 km (0.4 mile) NNW of Sage Hill (coordinates of record), on a private lease within a National Forest area. Discovered in 1880. First produced in 1917. Operated by L.G. Embree, California (1942-1943). This mine has been idle since 1943. MRDS database stated accuracy for this location is 10 meters.
NOTE: This is one of many localities placed into a very large area termed the "Forest Hill Divide area" by Rynearson. That area is based on geological and topographic considerations versus mining districts and overlaps several defined districts.
Mineralization is hosted in dunite. The ore body strikes N00S and dips 00N at a thickness of 5 meters, a width of 60 meters and a length of 240 meters. Ore body No. 1 is lenticular, disseminated; No. 2 is tabular; and, No. 3 is "other." The primary mode of origin was magmatic segregation. Primary ore control was lithology and secondary control was fracturing. Wallrock alteration is intense (carbonitization, silicification). Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).
Workings include surface and underground openings. The surface openings include an open pit wioth gophering.
Regional and local geologic structure: Lies in proximity to the Melones Fault Zone.
Production data is found in: Rynearson, Garn Arthur (1953).
The average grade of ore shipped during the period 1942 to 1943 was 40.64% Cr2O3, 12.23% Fe with an Fe:Cr ratio of 2.27.
There are no estimates of reserves in the literature. No ore in place was seen at the mine.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsMineral List
Mineral list contains entries from the region specified including sub-localities4 valid minerals. 1 erroneous literature entry.
Detailed Mineral List:
| ⓘ Antigorite Formula: Mg3(Si2O5)(OH)4 |
| ⓘ 'Chlorite Group' |
| ⓘ Formula: Fe2+Cr3+2O4 Localities: |
| ⓘ 'Fayalite-Forsterite Series' |
| ⓘ Magnesiochromite Formula: MgCr2O4 |
| ⓘ Magnetite Formula: Fe2+Fe3+2O4 |
| ⓘ 'Pyroxene Group' Formula: ADSi2O6 |
| ⓘ 'Serpentine Subgroup' Formula: D3[Si2O5](OH)4 |
| ⓘ Uvarovite Formula: Ca3Cr2(SiO4)3 Description: Comprises main part of matrix of some ore. |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Chromite ? | 4.BB.05 | Fe2+Cr3+2O4 |
| ⓘ | Magnesiochromite | 4.BB.05 | MgCr2O4 |
| ⓘ | Magnetite | 4.BB.05 | Fe2+Fe3+2O4 |
| Group 9 - Silicates | |||
| ⓘ | Uvarovite | 9.AD.25 | Ca3Cr2(SiO4)3 |
| ⓘ | Antigorite | 9.ED.15 | Mg3(Si2O5)(OH)4 |
| Unclassified | |||
| ⓘ | 'Chlorite Group' | - | |
| ⓘ | 'Fayalite-Forsterite Series' | - | |
| ⓘ | 'Pyroxene Group' | - | ADSi2O6 |
| ⓘ | 'Serpentine Subgroup' | - | D3[Si2O5](OH)4 |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Antigorite | Mg3(Si2O5)(OH)4 |
| H | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| O | Oxygen | |
| O | ⓘ Antigorite | Mg3(Si2O5)(OH)4 |
| O | ⓘ Chromite | Fe2+Cr23+O4 |
| O | ⓘ Magnesiochromite | MgCr2O4 |
| O | ⓘ Magnetite | Fe2+Fe23+O4 |
| O | ⓘ Uvarovite | Ca3Cr2(SiO4)3 |
| O | ⓘ Fayalite-Forsterite Series | |
| O | ⓘ Pyroxene Group | ADSi2O6 |
| O | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| Mg | Magnesium | |
| Mg | ⓘ Antigorite | Mg3(Si2O5)(OH)4 |
| Mg | ⓘ Magnesiochromite | MgCr2O4 |
| Mg | ⓘ Fayalite-Forsterite Series | |
| Si | Silicon | |
| Si | ⓘ Antigorite | Mg3(Si2O5)(OH)4 |
| Si | ⓘ Uvarovite | Ca3Cr2(SiO4)3 |
| Si | ⓘ Fayalite-Forsterite Series | |
| Si | ⓘ Pyroxene Group | ADSi2O6 |
| Si | ⓘ Serpentine Subgroup | D3[Si2O5](OH)4 |
| Ca | Calcium | |
| Ca | ⓘ Uvarovite | Ca3Cr2(SiO4)3 |
| Cr | Chromium | |
| Cr | ⓘ Chromite | Fe2+Cr23+O4 |
| Cr | ⓘ Magnesiochromite | MgCr2O4 |
| Cr | ⓘ Uvarovite | Ca3Cr2(SiO4)3 |
| Fe | Iron | |
| Fe | ⓘ Chromite | Fe2+Cr23+O4 |
| Fe | ⓘ Magnetite | Fe2+Fe23+O4 |
| Fe | ⓘ Fayalite-Forsterite Series | |
Other Databases
| Link to USGS MRDS: | 10077039 |
|---|
Localities in this Region
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 #0060610527
