| Basis for focus area |
Focus area based on the Sunshine mining district outline from Krahulec (2018b) and expanded to include similar geology clay deposits hosted in the same stratigraphic unit as the scandium-bearing clay deposits. |
| Identified resources |
Historical production of scandium. |
| Production |
Variscite discovered at the Little Green Monster in 1893, and from 1894 to 1911 variscite mined as a gemstone. In 1959 and 1960, miners produced two shipments of crandellite ore, weighing 330 and 4000 lbs, which contained 0.14% and 0.10% Sc2O3 respectively (Shubat, 1988). |
| Status |
Past mining. |
| Estimated resources |
Unknown. |
| Geologic maps |
Clark and others (2012), scale 1:62,500. |
| Geophysical data |
Inadequate Rank 4 aeromagnetic coverage. |
| Favorable rocks and structures |
Dark limestone and black shale of the Upper Mississippian Great Blue Limestone, stratigraphically above the Long Trail Shale Member. Clay Canyon has an unnamed shale in the upper Great Blue Limestone that has been variably altered to clay, including illite, kaolinite, halloysite, smectite, variscite, and crandallite. |
| Deposits |
Little Green Monster. |
| Evidence from mineral occurrences |
UMOS (Utah Geological Survey, 2021). |
| Geochemical evidence |
Clay Canyon crandallite contains Sc2O3 over a range of 100 to 8000 ppm; wardite, deltaite, and goyazite contain as much as 5000 ppm Sc2O3. Scandium enrichment accompanied alteration of variscite to crandallite and other late-stage minerals. Bulk samples of crandallite ore contained over 1000 ppm Sc2O3. Trace elements associated with scandium mineralization include Sr, Y, Ga, And V (Shubat, 1988). Very limited geochemical sampling of the clay mines showed weak Au to 0.09 ppm, As to 74 ppm, Sb to 29 ppm, and Zn to 590 ppm (Krahulec, 2018b). |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
See Krahulec (2018b) and Shubat (1988). |
| Comments |
This district is very understudied despite being proximal to so many major mineralization centers (for example, Mercur and Bingham) and having unique mineralization and a distinct critical mineral signature. There is no mineral system/deposit type that accurately captures this area, though there may be multiple mineralizing events. Shubat (1988) notes that the first event in the mineralization process was replacement of limestone by variscite, followed by crandallite replacing the variscite. Precipitation of rare Sc-bearing Al phosphate minerals both accompanied and post-dated crandallite alteration. Quartz, calcite, and limonite precipitation followed the phosphate minerals. |
| Cover thickness and description |
Unknown. |
| Authors |
Stephanie Mills. |
| New data needs |
Regional aeromagnetics and aeroradiometrics survey; airborne hyperspectral would be useful in this area given the clay content; detailed mapping. |
| Geologic mapping and modeling needs |
1:24,000 scale mapping. |
| Geophysical survey and modeling needs |
High-resolution, Rank 1 aeromagnetic and radiometric surveys. |
| Digital elevation data needs |
Lidar complete. |
