White Mountain Mine, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
White Mountain Mine	Mine
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

A Hg-Sb occurrence/mine located in the centeer NE¼SW¼ sec. 7, T24N, R30W, Seward Meridian, on Bureau of Land Management administered land (private lease). The USGS MRDS database stated accuracy for this locality is 500 meters.

Location: The White Mountain Mine is located on a southwest facing slope on the north side of the headward reaches of the Cheeneetnuk River at an elevation of approximately 2,000 feet (610 m). The term White Mountain was originally used by local residents to refer to a prominent mountain two miles directly west of the mine that is capped by white dolomite of Late Silurian age (Gilbert, 1981). ? The White Mountain Mine correlates with locality number 14 on Cobb (1972), and located just to the southeast of the airstrip marked on the McGrath A-4 quadrangle and McGrath 1:250,000 quadrangle maps. (Note that White Mountain Mine is misplotted on the Lime Hills 1:250,000 quadrangle map). Location is accurate; the reporter has visited the site numerous times since 1977. The 700 meter long airstrip is now largely overgrown with vegetation and suitable only for small 'Super Cub' type aircraft.

Geology: A Hg-Sb deposit (Mineral occurrence model information: Model code: 177; USGS model code: 27a; Deposit model name: Hot-spring Hg). The White Mountain Mercury Mine consists of a series of at least three discrete, structurally controlled, cinnabar-dolomite-chalcedony mineralized areas with subordinate to trace amounts of stibnite, pyrite, calcite, and dickite. During development and production activities, the three mineralized areas were designated the 'South', 'Center', and 'North' ore zones (Sainsbury and MacKevett, 1965). The cinnabar deposits are distributed along a belt approximately one kilometer wide and three kilometers long near the northwest side of the active strand of the Farewell-Denali Fault system (Gilbert, 1981). In the White Mountain Mine area, this fault system juxtaposes Cambro-Ordovician ollitic limestone on the southeast against Ordovician mudstone on the northwest (Gilbert, 1981). Both units are part of the Nixon Fork subterrane (Decker and others, 1994). The cinnabar ore bodies are found near individual strands of the Farewell-Denali fault, generally where shale is faulted against limestone (Sainsbury and MacKevett, 1960, 1965). All of the known ore zones strike from N25W to N40E and dip steeply to vertically, parallel to the Farewell-Denali fault system. ? In all three mineralized areas, cinnabar occurs as dark-red crystals coating open-space fillings in brecciated dolomite, as 'paint' on breccia surfaces, and as irregular veinlets of nearly pure cinnabar. Dolomite replacement is a conspicuous feature of the ore zones and in addition, significant amounts of chalcedonic alteration also occurs in the north ore zone. These features, coupled with observations of ancestral spring activity in other nearby deposits such as the Peggy Barbara (MG026) and Mary Margaret Prospects (MG027) and isotopic data from White Mountain Mine (Gray and others, 1997) suggest a mineralogical origin in a hot springs environment. Crystalline cinnabar was especially well developed in the North ore zone.? In the South ore zone a 60 meter long ore body 12 meters wide contained as much as 1 percent mercury. In the Central deposit, an elliptically shaped, 10 meter by 13 meter zone of cinnabar mineralization was intersected to a depth of 23 meters. The North zone is at least 76 meters long and 3 to 6 meters wide, and contains some of the richest ore with grades over 2.5 meter widths exceeding 5 percent mercury (Sainsbury and MacKevett, 1965; Conwell, 1975). Local alteration includes extensive dolomitic and chalcedonic alteration; minor dickite, limonite, and calcite alteration. Local rocks include rocks of the Novi Mountain and Telsitna Formations, and unnamed correlative units, massive dolomite and limestone, Late to Middle Ordovician.

Workings/Exploration: Cinnabar mineralization in the White Mountain area was discovered by Jack Egnaty in 1958, while following up panned cinnabar concentrates in the upper Cheeneetnuk River area. The prospects were taken over by Cordero Mining Company (R.F. Lyman family) in 1959 (Jasper, 1961). Trenches were quickly made by Cordero Mining Company and mapped by the U. S. Geological Survey (Sainsbury and MacKevett, 1960, 1965). In 1960, the U.S. Bureau of Mines completed additional trenching and hand tested specific areas with an auger drill (Malone, 1962, 1965). The U.S. Geological Survey visited the property again in 1961 and completed additional mapping of exposed trenches (Sainsbury and MacKevett, 1965). ? After production was initiated in 1964, Cordero Mining Company continued exploration and development of the property through limited diamond drilling, trenching,shaft sinking, and drifting. Their activities continued until the mine ceased operations in 1974 (Conwell, 1975). ? In the South ore zone, a 60 meter long ore body 12 meters wide contained as much as 1 percent mercury. In the Central deposit, an elliptically shaped zone an 10 meter by 13 meter area contains cinnabar mineralization. Drilling confirmed the presence of cinnabar to a depth of 23 meters. The North zone is at least 76 meter long and 3 to 6 meter wide and contains some of the richest ore on the property with grades over 2.5 meter widths exceeding 5 percent mercury.(Sainsbury and MacKevett, 1965; Conwell, 1975).

Production: Production began in 1964 from a series of small open pits and trenches. Later in 1967 and 1968, shallow underground workings were mined (Conwell, 1971). Originally rich ores were selectively mined and shipped for processing and retortion to a facility in Oregon. In 1971, a small crusher and concentrator were designed to process lower grade disseminated ores on the mine site and to produce a cinnabar crystal concentrate for selected buyers. The ores were mainly retorted at a facility in Oregon. the White Mountain Mine is estimated to have produced about 3,500 flasks (58,300 kilograms) of mercury from 1964 to 1974 (Bundtzen and Conwell, 1982). Operations ceased when mine operator Robert F. Lyman was killed in a heavy equipment accident at the mine site (Conwell, 1975; Bundtzen and Conwell, 1982). The property has remained inactive since.

Other Databases

Link to USGS MRDS:	10002600
Link to USGS MRDS:	10234210
Link to USGS - Alaska:	MG025

Other Regions, Features and Areas containing this locality

References