Granite County Montana Gold Production
The First Chance (Garnet) district is in northern Granite County in the drainage basin of Bear Creek, a tributary of the Clark Fork River. Both placer and lode deposits were found in the district. The placer deposits along Bear Creek and its subsidiary gulches were the most productive in Granite County and were among the more productive of the early placer, operations in Montana. The placer deposits were discovered in 1865, and up to 1917, according to Pardee (1918, p. 231-232), they produced gold valued between $5 million (241,900 ounces) and $7 million (338,660 ounces), mostly in the first few years of operation. From 1917 through 1959 the district produced a minimum of 15,200 ounces, most of which was mined during the period 1939-42. The total placer production from the district through 1959 was between 260,000 and 355,000 ounces.
The lode deposits are valuable chiefly for gold, but some copper and silver have also been produced. The first lodes were located in the district in 1867 but were not exploited to any extent until 1896 (Pardee, 1918, p. 171-172). A continuous but fluctuating production was maintained through 1942. After World War II the district had only minor activity and was virtually idle through the 1950's. The total lode gold production through 1959 was probably 85,000 to 90,000 ounces. The total lode and placer production combined is probably between 345,000 and 445,000 ounces.
The rocks of the Garnet district are quartzite and shale of the Belt Series of Precambrian age overlain by limestone of Paleozoic age. These rocks were folded into a northwest-trending arch and were intruded by a mass of granodiorite of Late Cretaceous or Tertiary age. The ore deposits are in veins in the granodiorite and along bedding planes in quartzite and schist. Quartz is the dominant vein mineral; barite and ankerite are locally abundant. The ore minerals are pyrite, tetrahedrite, chalcopyrite, galena, and in rare occurrences, gold tellurides and molybdenite. Most of the gold is associated with pyrite (Pardee, 1918, p. 172-177).