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.
Investigate Gold Mining at the Zortman-Landusky Mine
- Landusky and Zortman Historic Context. This Montana Department of Environmental Quality webpage provides information about gold mining at the Landusky and Zortman mines. The webpage concentrates on the historic context of the mining from the early discovery of gold in the 1800s, through several cycles of boom and bust. A brief description of the geology of the gold deposits is given. Also provided is the history of selected mines including the Gold Bug Mine, the August Mine, the Little Ben Mine, and the Ruby Gulch Complex. (more info)
- Technical Resource Document: Extraction and Beneficiation of Ores and Minerals
Volume 2: Gold. This EPA document provides detailed information about the gold mining industry in terms of the wastes associated with gold mining and processing. The report briefly characterizes the geology of gold ores and the economics of the industry. Specific information from EPA site visits is included for the Brewer Mine, Colosseum Mine, Nerco Minerals Cripple Creek, and the Newmont Gold Company in Nevada. (more info)
- Zortman, Landusky: Gold. This Porter GeoConsultancy webpage describes the gold and silver deposits at Zortman and Landusky in north central Montana. Early exploration and development history of gold and silver in the Little Rocky Mountains, and the geology of this area are discussed. (more info)
- Gold Deposits of Zortman-Landusky, Little Rocky Mountains, Montana. [Hastings, 1988] This paper discusses the history and development of the gold deposits of the Zortman-Landusky mine. Geologic information is provided about the regional setting, structural geology, sedimentary rocks, igneous rocks, and ore deposits of the area. Many figures accompany the text, including a geologic map and stratigraphic column of the Little Rocky Mountains. (citation and description)
- Mineral Resources, Economics and the Environment. [Kesler, 1994] This is a textbook that covers mineral resources, economics and the environment. (citation and description)