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Exploration of the Rio Tinto Gossan, Northeastern Nevada: How Prospector S. Frank Hunt Discovered the Mountain City Copper Mine
This paper describes the discovery and economic geology of a high grade secondarily enriched copper deposit near Mountain City, Elko County Nevada, It is based largely on contemporary written accounts and the recollections of people acquainted with this slowly evolving success story of 1919-1932.
The methods by which prospectors achieved success (a rare event) in the eastern Great Basin of western Utah and eastern Nevada changed with time. By the 1920s, finding new mineralized areas was becoming difficult. Many new tools also appeared, but most were little known or unaffordable to the traditional prospector. S. Frank Hunt, a “prospector-geologist” with perhaps a year of formal education beyond high school, sought metallic ore in western Utah and eastern Nevada for about 35 years. The keys to his eventual success included occasional infusions of academic and practical learning, often separated by years of work in the desert. These, a few mentors and relationships, extensive literature study, and great persistence proved essential to his discovery of an important copper deposit in 1932.
In 1919 Hunt defined and staked a possible target, beneath unusual barren gossan he found on an old prospect dump near Mountain City Nevada. His exploration program in this remote area focused on less than 40 acres of National Forest land, but its execution required 13 years of frustration and fund seeking. Assorted companies and experts rejected the prospect, because the barren-looking outcrops Hunt described as a leached capping was outside their experience in copper exploration. Most rock in his tunnels and test holes contained no trace copper. They also saw no reason to expect big copper deposits in this old quartz vein silver and gold district. A chance review of some hand samples by Reno Sales, Chief Geologist of Anaconda Copper Co., was a factor in keeping optimism alive. Hunt was 68 years old when his −63 degree inclined prospect shaft finally cut ore at 218 feet beneath the capping area in 1932. The vertical transition from a ferruginous gossan virtually lacking in copper to a thick chalcocite and oxide blanket assaying about 47% copper occurred in less than one foot.
Exploration funding came from private individuals and an innovative public-company financing in Salt Lake City. When the ore body was struck an Anaconda Copper subsidiary, International Smelting and Refining Company, out-negotiated competitors and bought control of the property for a high price. During 15 years of operation, the Mountain City mine yielded 216 million pounds of copper metal, 304 thousand ounces of silver, and 6300 ounces of gold. The ore grades were economic at any imaginable copper price. Shipments to the Anaconda-controlled Tooele copper smelter helped keep that labor-intensive Utah enterprise alive during the Depression, when lower grade copper mines ceased or curtailed operations.
During winter seasons, Hunt documented aspects of his knowledge and thinking in a series of essays, published between 1921 and 1928. In 1936 he collected them into a volume he titled Mining Geology Outlined. Of most interest here are his philosophical views of exploration, which changed with the times. As he grew older and more infirm, he worried about becoming a “dinosaur”. By age 65, with diminishing hope of testing his target at Mountain City, he expressed both stoicism and near-desperation. In 1931, with the Great Depression stifling exploration funding, a partner found a unique way to raise money to test his idea. At age 68, Hunt was suddenly a multi-millionaire.
Future prospectors must be students of economic geology, Hunt contended. To succeed, one must combine clear understanding of science with extensive observation in the field. Metal shortages would assure the future of such prospectors. To help train future ore finders through field study in the Great Basin, he donated significant funds, stock, and exploration gear to the S. Frank Hunt foundation at the Mackay School of Mines at the University of Nevada (Reno).
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