| Basis for focus area |
Barite occurrences and production within limestone replacement deposits within the Calaveras Formation. |
| Identified resources |
Historical production of barite. |
| Production |
Savercool (1946-1953): 20,000 tons barite; Synthetic Iron Company mine (1932-1936): 17,000 tons barite; Democrat mine (1930-1945): 35,000 tons barite; Spanish mine (1930-1945): 35,000 tons barite; El Portal mine (1910-1948): 400,000 tons barite; Devils Gulch mine (1937?-1961?): 100-100,000 tons barite. |
| Status |
Past mining; no current mining or exploration. |
| Estimated resources |
Unknown. |
| Geologic maps |
Jennings and others (1977), scale 1:750,000; California Geological Survey Regional Geologic Maps and Geologic Atlas of California, scale 1:250:000. |
| Geophysical data |
Inadequate Rank 3 to 4 aeromagnetic and Rank 4 aeroradiometric coverage. |
| Favorable rocks and structures |
Limestone beds within the Calaveras Formation and age equivalents. |
| Deposits |
Savercool (MRDS dep_id: 10110889), Synthetic Iron Company mine (MRDS dep_id: 10115628), Democrat barite (MRDS dep_id: 10109286), Spanish mine (MRDS dep_id: 10310686), El Portal barite mine (MRDS dep_id: 10109245), Devils Gulch (MRDS dep_id: 10031291). |
| Evidence from mineral occurrences |
MRDS. |
| Geochemical evidence |
The composition of the ore at the El Portal mine was 85% barite, 2 to 3% witherite, 0.5% pyrite, and 12 to 13% silica (Brobst, 1958). |
| Geophysical evidence |
None. |
| Evidence from other sources |
None. |
| Comments |
The deposit at El Portal, Mariposa County yielded about 75% of the barite mined in California and most of the witherite mined in the United States (Brobst, 1958). See adjacent and overlapping focus areas for Orogenic, Mafic magmatic, and Volcanogenic Seafloor mineral systems. |
| Cover thickness and description |
Bedrock exposure at the surface. |
| Authors |
Catherine Wesoloski. |
| New data needs |
High resolution geophysics, geologic mapping, lidar. |
| Geologic mapping and modeling needs |
1:24,000 scale geologic mapping. |
| Geophysical survey and modeling needs |
High resolution, Rank 1, aeromagnetic surveys would be useful in delineating serpentine, ultramafics, but unclear if a new geophysical survey would be effective for barite deposits. |
| Digital elevation data needs |
Lidar partial coverage, mostly from wildfires; needs full coverage. |
