By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Prospectors, drawn to central Idaho by the rich gold strikes in the Boise Basin in 1862, went from there into what is now Blaine County. Silver-lead deposits were found in the Wood River region in 1864, but these were ignored for a few years, because the chief interest was in gold (Umpleby and Ross, in Umpleby and others, 1930, p. 81). Gold deposits in the Camas district southwest of Hailey were developed in 1879. By 1880 the Wood River silver-lead deposits were worked, and gold was yielded as a byproduct. A decline in mining in the county began in the early 1900's and, except for a few brief revivals, continued until the early 1940's, when a period of high productivity of base-metal ores with gold as a byproduct commenced. Mining in the county slowly declined from the late 1940's through 1959.
Production of gold from 1874 through 1942 was 176,262 ounces (Staley, 1946, p. 13) ; total production from 1874 through 1959 was 212,638 ounces.
The Camas (Hailey, Mineral Hill) district is in west-central Blaine County, 5 to 15 miles southwest of Hailey in T. 1 N., Rs. 16 and 17 E.
Gold was first discovered in this district in 1865 at the site of the Camas 2 mine, but there was no production until 1879 (Anderson and Wagner, 1946, p. 9). Other discoveries were made in 1880, and the period from 1880 to the early 1900's was one of great prosperity in the district. The chief mine, the Camas 2, produced ore valued at $1 1/4 million before it was closed in 1898 (Anderson and Wagner, 1946, p. 9). Most of the mines in the district remained closed, but the Camas 2 and the Hattie were reopened for short periods in the 1930's, 1940's, and 1950's.
Production records are not complete, especially for the years of peak activity before 1900. Of the 175,770 ounces of gold produced in Blaine County from 1874 to 1900, Anderson and Wagner (1946, p. 9-10) estimated that more than half of it came from the Camas district. Umpleby and Ross (in Umpleby and others, 1930, p. 84) listed a total of 7,019 ounces produced from the Mineral Hill camp between 1902 and 1926; 7,161 ounces were produced from 1932 through 1959. Total gold production, including the estimate of Anderson and Wagner (1946, p. 9), was about 102,000 ounces. Much silver, lead, and zinc was mined also.
The district is underlain by granodiorite and quartz monzonite of the Idaho batholith of middle Cretaceous age, which is cut by many aplite and pegmatite dikes and a few lamprophyre dikes (Anderson and Wagner, 1946, p. 4-9). Remnants of a once-extensive cover of Tertiary basalt that buried an erosion surface carved into the granitic rock are found at a few places. The gold occurs in quartz veins along gently dipping faults in the batholith. The veins are generally rich in silver and carry two to four times as much silver by weight as gold. Some contain moderately large amounts of sulfides (Anderson and Wagner, 1946, p. 10).
In the northeastern part of the district, near Hailey, the country rock consists of tightly folded Paleozoic sedimentary rocksâ€”the Milligen (Missis-sippian and Devonian) and the Wood River (Pennsylvanian) Formations. These have been faulted and intruded by several stocks, which are probably related to the Idaho batholith (Ross, 1941, p. 13). Most of the deposits are in shear zones in the Mis-sissippian sedimentary rocks, which largely are thin-bedded carbonaceous argillites. The ore minerals are argentiferous galena, sphalerite, and tetrahedrite, with minor pyrite in a gangue of altered and crushed country rock, siderite, and a little quartz (Ross, 1941, p. 13).
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