Gravel Range Mining District (Singheiser Mining District), Lemhi County, Idaho, USAi

Regional Level Types
Gravel Range Mining District (Singheiser Mining District)	Mining District
Lemhi County	County
Idaho	State
USA	Country

The Gravel Range District covers a loosely defined area which includes the headwaters of Moyer Creek, Panther Creek, and Silver Creek. The district is bound on the northeast by the Blackbird District and on the northwest by the Yellowjacket District.

Mineralization in the district generally consists of two types; fluorspar bearing veins, lenses, and replacements and precious metal-bearing veins. Both types occur in volcanic rocks. The Singheiser deposit consists of a 40-foot wide, northeast trending shear zone which contains a 3 to 8-foot-thick quartz vein and numerous quartz veinlets. Shortly after 1896, a 50 ton per day mill was built to treat the ore. Development at the time of Umpleby's visit consisted of perhaps 3,000 feet of workings (Umpleby, 1913, p. 176). According to USBM production records, the mine produced significant amounts of silver, copper, and gold between 1907 and 1974.

At the Rabbit Foot mine, located about 3 miles northeast of the Singheiser, a 10-stamp mill operated during the early 1900's. Mineralization also consists of quartz lenses and stringers in shear zones in volcanic rock. According to Umpleby (1913, p. 177), development consisted of 5,000 feet of workings.

The Meyers Cove fluorspar deposits gained recognition during the early 1940's. During 1944, Chamac Mines completed a 100-ton flotation plant and a six-day test run was conducted in September. However, due to poor market conditions, actual mining did not start in ernest until 1951. During the next two years, 37,432 tons of fluorspar-bearing rock was mined from six deposits and delivered to the mill. From this tonnage, 10,979 tons of acid grade, 998 tons of ceramic grade, and 100 tons of metallurgical grade fluorspar was recovered. Most of this production came from the Big Lead deposit (Anderson, 1954, p. 10).

Between 1954 and 1972, the Meyers Cove deposits were worked intermittently by the Seaforth Mining Company and an additional 25,000 to 30,000 tons of metallurgical grade ore was produced (Fisher and Johnson, 1987, p. 140).

Most of the fluorspar is coarsely crystalline and occurs as veins, lenses, crusts around fragments of rocks, and replacements in shear zones in Challis volcanic rocks. The deposits developed through 1954 averaged 4 to 5 feet thick and 100 to 300 feet long. At the Big Lead deposit, the main body of fluorspar is 300 feet long and up to 18 feet wide. It trends from northwest to nearly west and dips southwest (Anderson, 1954, p. 19).

Fluorspar resources in deposits held by the Seaforth Mining Company during 1985 were estimated to be 1,000,000 tons averaging approximately 35 percent fluorite. U.S. Geological Survey personnel conclude that with adequate exploration, additional resources of the same magnitude could be delineated (Fisher and Johnson, 1987, p. 144).