| Basis for focus area |
Focus area includes Harney Peak granite and surrounding pegmatites and veins and shear zones that cut Precambrian metasedimentary rocks. Area encompasses beryl occurrences in MRDS. |
| Identified resources |
Historical production of beryllium (beryl), feldspar, and mica. |
| Production |
About 4,200 tons of beryl was produced from Black Hills pegmatites between 1879 and 1958. In 1943, 130 tons of beryl ore were produced, averaging 11.85% BeO. |
| Status |
Past mining. |
| Estimated resources |
A number of small pegmatites contain some beryl, but are not an important source of beryllium at this time. |
| Geologic maps |
Redden and DeWitt (2008), scale 1:100,000; Redden and others (2010), scale 1:24,000; Wilson and DeWitt (1995), scale 1:100,000; DeWitt and others (1986), scale 1:250,000; Martin and others (2004), scale 1:500,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
More than 22,000 pegmatites have been recognized in the area of the Harney Peak granite, many cutting surrounding metasedimentary rocks. |
| Deposits |
Helen Beryl (MRDS dep_id: 10104268), Elkhorn mine (MRDS dep_id: 10055780), Tin Mountain mine (MRDS dep_id: 10104256). |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
NURE stream sediment data in the Harney Peak area are enriched in Li and U, but sample density it too low to identify targets. |
| Geophysical evidence |
No data. |
| Evidence from other sources |
No data. |
| Comments |
Primary commodities at the Tin Mountain pegmatite mine (MRDS dep_id10104256) are cesium, lithium, feldspar, and mica. |
| Cover thickness and description |
Most pegmatites and veins exposed at the surface. |
| Authors |
Laurel G. Woodruff, Benjamin J. Drenth, Darren J. Johnson. |
| New data needs |
New geological mapping for areas not currently covered by 1:24,000 scale mapping, geochemical data. |
| Geologic mapping and modeling needs |
Recent detailed geologic mapping, some at 1:24,000 scale. |
| Geophysical survey and modeling needs |
Geophysical methods not useful for pegmatite deposits. |
| Digital elevation data needs |
Lidar adequate. |
