| Basis for focus area |
Multipart focus area composed of graphite mineral sites surrounded by a 5 km buffer. In Robinson and others (2017), two past producers (from north to south) are Black Diamond Carbon Graphitic and Crystal Graphite mine. Black Diamond Carbon Graphitic is listed as flake and Crystal Graphite mine is listed as lump or flake. In MRDS, several additional past producers (United Minerals Co. Mill, Birds Nest Graphite Deposit), prospects, occurrences, and unknowns are listed. Associated with metamorphic rocks in Montana on state geologic map compilation (Horton and others, 2017). |
| Identified resources |
Historical production of graphite. |
| Production |
The Crystal Graphite mine (lump) began operation in 1902, total production was about 2,200 tons graphite, and no production after 1948 (Cameron and Weis, 1960; Weis, 1963). |
| Status |
Past mining. |
| Estimated resources |
Unknown. |
| Geologic maps |
Raines and Johnson (1996), scale 1:500,000. |
| Geophysical data |
Inadequate aeromagnetic and aeroradiometric coverage. |
| Favorable rocks and structures |
Shear zones in lower Paleozoic gneiss. |
| Deposits |
Black Diamond Carbon Graphitic (MRDS dep_id: 10173269), Crystal Graphite mine (MRDS dep_id: 10070489; USMIN Site_ID: MT00008), Birds Nest Graphite (MRDS dep_id: 10010811). |
| Evidence from mineral occurrences |
MRDS; USMIN; Robinson and others (2017). |
| Geochemical evidence |
Unknown. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
The Black Diamond graphite deposit is a metamorphosed coal seam at the top of the Morrison Formation, overlain by the Kootenai Formation. The metamorphosed coal seam is black, earthy, internally contorted with numerous metallic-lustered slickensides. The seam is underlain by hard, sheared claystone and overlain by hard, black, shattered and sheared shale and mudstone. At the Crystal Graphite mine, graphite occurs in veins in gneiss and disseminations in pegmatite. |
| Cover thickness and description |
Metamorphic and Mesozoic granitic rocks (Horton and others, 2017). |
| Authors |
David A. Ponce. |
| New data needs |
Re-evaluate deposit, geological mapping, lidar. |
| Geologic mapping and modeling needs |
Detailed geologic mapping. |
| Geophysical survey and modeling needs |
High resolution aeromagnetic and radiometric coverage. Graphite is unusually highly conductive and magnetotelluric surveys may be useful. |
| Digital elevation data needs |
Lidar incomplete. |
