Exploration and Development History of Gold Mining at the Zortman-Landusky Mine
Gold was first discovered near the Fort Belknap Indian Reservation in the Little Rocky Mountains in the late 1880's by prospectors from the Black Hills. Only minor placer gold were exploited, although the source lodes were soon found and mining commenced shortly thereafter, first in the Landusky area and then at Zortman. Development of the vein deposits accelerated in the early 1900's with the dawn of cyanide processing, and continued into the 1920's when the operation became marginal, with sporadic working until 1959. More recently a number of the major companies have explored in the area. Pegasus Explorations Ltd commenced development of the shallow, low grade stock work mineralization in 1979. Cyanide heap leach gold mining began in 1980 with 1.18 mt of ore being mined to produce 1.06 t Au and 1.65 t Ag. By 1985 the annual mining rate was 4.85 mt of ore, yielding 1.88 t Au and 4.90 t Ag (Hastings, 1988). In 1994 13.46 mt of ore were treated to produce 3.35 t Au at a cost of $US 9.75/g Au [$US 303/oz] (AME, 1995). (Zortman, Landusky: Gold (more info) ).
In the late 1800's, the Gros Ventre and the Assiniboine opposed the "sale of the mountains," which was advocated by federal commissioners who were assigned to negotiate the sale of the gold-mining country in 1896. By advising the impoverished Indians that they would starve in two years if they did not make an agreement with the government, the commissioners convinced tribal representatives to sell a strip of land, seven miles long and four miles wide, for $360,000. Pegasus Gold Company now mines this site, with heavy opposition from some tribal members. The opposition is compounded by the current reality of contaminated land and water and the accompanying health risks to the reservation people.
Gold production increased sharply in the late 1980's due to the use of heap leach gold mining to extract gold. This involves the placement of the ore on heap leach pads and spraying cyanide onto the ore to extract the gold. The Zortman mine was the first major heap leach gold mine in the United States. Click here (more info) to view a graph that provides information about U. S. gold production from the 1840's to the 1990's.