![]() ![]() Homestake ore is virtually entirely contained in a unit of iron-formation locally known as the Homestake Formation, which seemingly had more gold in the original sediments than similar rocks exposed elsewhere in the Black Hills. ![]() Current opinion is that (1) the Homestake ore is mainly Precambrian, (2) a trivial amount of Homestake ore is Tertiary, (3)gold in Deadwood basal conglomerate is largely of placer origin, and (4) the gold of replacement deposits in the Deadwood and in other rock units came originally from sources similar to the Homestake deposit or its parent materials. Obviously, any exploration program should be aimed at finding a new deposit resembling the Homestake in the Precambrian, but discovery in the Deadwood of a new group of ore bodies containing several hundred thousand ounces of gold would certainly be worthwhile.Įvidence has long been available that the Deadwood deposits and the Homestake deposit are somehow related. Efforts to find totally new deposits have been modest and sporadic no comprehensive and systematic program has ever been attempted. Elsewhere, prospecting has been intense, both in the Precambrian rocks, which are exposed over an area 61 by 26 miles (98 by 42 km), and in nearby Paleozoic rocks.Īll the known ore bodies have been found either at the surface or in subsurface workings of operating mines. About 99 percent of the total production has been within a radius of 5 miles (8 km) of Lead. ![]() Most of the rest has come from ore deposited in the Deadwood Formation (Cambrian) by hydrothermal replacement during early Tertiary igneous activity. Of the recorded production of 34,694,552 troy ounces of gold mined in South Dakota through 1971, about 90 percent has come from Precambrian ore bodies in the Homestake mine at Lead in the northern Black Hills. ![]()
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