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Eldorado Bar deposit (Eldorado Strip Mine), Eldorado Bar, East Helena, Lewis and Clark Co., Montana, USA
Hematite
Eldorado Bar deposit, Eldorado Bar, East Helena, Lewis and Clark Co., Montana, USA
Photo: Rob Lavinsky
Eldorado Bar deposit, Eldorado Bar, East Helena, Lewis and Clark Co., Montana, USA
Photo: Rob Lavinsky
Latitude: 46°44'10"N
Longitude: 111°51'6"W
Longitude: 111°51'6"W
Mineralization is a Au-PGE-gemstone deposit hosted in Holocene gravels. The ore body is river sands and gravels with a depth-to-top of 4.57 meters. Local rocks include Mississippian, undifferentiated (Greyson shale).
Workings included surface alluvial mining operations. 10 million cubic yards of material were handled in 6.5 years. WGM was conducting initial tests for renewed sapphire mining in this area in September 1994.
Production data are found in: Mertie (1951): 80.
Production statistics: Year 1944; Period 1938 - 1944; Material: gravel: ore mined: more than 10,000,000 cubic yards: at $0.20/cubic yard (period values).
Comments on the production information: 0.006 ounces Au/ton.
Reserve-Resource data are found in: The Northern Miner (1994).
Analytical data results: Per 100 pounds of concentrates: Pt = 7.86 ounces; Os - Ir = 0.56 ounces and Pd = 0.42 ounces.
Mineral List
| Almandine Cassiterite Corundum | Corundum var: Sapphire 'Garnet' Gold | Hematite Kyanite Quartz var: Chalcedony | Topaz |
10 entries listed. 7 valid minerals.
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References
Montana Bureau of Mines & Geology (1948), Memoir 26: 68-69.
Mertie, J. B., Jr., et al (1951), Geology of Canyon Ferry, Montana, USGS Bulletin 972: 79-80.
Montana Bureau of Mines & Geology Bulletin 100 (1976): 36.
The Northern Miner (1994), American Gem Producing Sapphires in Montana: 80(30): 1, 10, 11.
Kievlenko, E.Ya. (2003), Geology of Gems: 70.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10038144 & 10124261.
Gobla, M.J. (2012), Montana mineral locality index, Rocks & Minerals: 87(3): 208-240.
U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0300490227.
Mertie, J. B., Jr., et al (1951), Geology of Canyon Ferry, Montana, USGS Bulletin 972: 79-80.
Montana Bureau of Mines & Geology Bulletin 100 (1976): 36.
The Northern Miner (1994), American Gem Producing Sapphires in Montana: 80(30): 1, 10, 11.
Kievlenko, E.Ya. (2003), Geology of Gems: 70.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10038144 & 10124261.
Gobla, M.J. (2012), Montana mineral locality index, Rocks & Minerals: 87(3): 208-240.
U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0300490227.
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