Mine, Inactive

Commodities and mineralogy

Main commodities Hg
Other commodities Ag; Au; Mo; Sb; Te
Ore minerals arsenopyrite; cinnabar; stibnite
Gangue minerals carbonate; quartz

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale C-8
Latitude 61.5963
Longitude -158.96837
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Kolmakof Mine is on a prominent terrace on the north bank of the Kuskokwim River about 3.0 mile northwest of the abandoned site of the Russian redoubt at Kolmakof and 1.5 mile west-northwest of VABM Sutter. The mine is at an elevation of about 320 feet in NE1/4 sec. 6, T. 17 N., R. 54 W., of the Seward Meridian. The mine is locality 27 of Miller and others, (1989). The location is accurate.

Geologic setting

Geologic description

The rocks in the vicinity of the Kolmakof mercury deposit consist of sandstone and shale of the Upper Cretaceous, Kuskokwim Group that have been intruded by complexly deformed mafic dikes, altered to a distinctive orange to tan silica-carbonate rock (Smith and Maddren, 1915; Cady and others, 1955; Jasper, 1961; Malone, 1962; Bundtzen and others, 1998). The altered dikes strike N45E and dip 40-60SE.
Mineralization consists of narrow stringers of bright red cinnabar, disseminated arsenopyrite, and minor stibnite in silica-carbonate breccias and fractures in the altered dikes. An adularia-bearing, chalcedonic alteration assemblage overprints small portions of the altered dikes in the pit that has been mined. Sulfide-bearing quartz-carbonate veins about 1 inch thick are in sandstone about 270 feet east east of the main mine workings. A few samples in the cinnabar-rich zones contain up to 0.29 ounce of gold per ton and 1.31 ounces of silver per ton ; however, most samples described by Bundtzen and others (1998) and Jasper (1955 [PE 82-4]) did not contain any significant gold or silver values. The quartz-carbonate veins also contain 27 to 66 parts per million (ppm) tellurium and 24 to 54 ppm molybdenum. Extensive channel sampling by Jasper (1955 [PE 82-4]) indicated grades of from 0.38 to 19.20 percent mercury over sample widths of from 22 to 50 inches. The total production of the Kolmakof Mine is about 250 flasks of mercury (about 19,000 pounds) (Bundtzen and others, 1998).
Geologic map unit (-158.970738618137, 61.5955868085981)
Mineral deposit model Silica-carbonate mercury (Cox and Singer, 1986; model 27c).
Mineral deposit model number 27c
Age of mineralization Probably Late Cretaceous (Bundtzen and Miller, 1997; Gray and others, 1997).
Alteration of deposit Mafic dikes are altered to silica-carbonate rock; adularia in mineralized zones.

Production and reserves

Workings or exploration Most of the following summarizes Bundtzen and others (1998). According to Spurr (1900), the Kolmakof mercury deposit was discovered by Russian traders in 1838, making it one of Alaska's earliest mineral discoveries. In 1881, George King explored the deposit and sank a short shaft. In 1901, Duncan McDonnell found new high grade mercury mineralization but did not develop the deposit. In 1908, Gordon Bettles explored the Kolmakof deposit with an adit and a shaft about 80 feet deep. The U.S. Bureau of Mines trenched and sampled the Kolmakof deposit in 1944 (Webber and others, 1947); in 1958 (Maloney, 1962); and in 1970 (Merrill and Maloney, 1974). Much work took place in 1944, when 29 trenches totaling 600 feet were cut (Webber and others, 1947). In 1958, 145 chip and channel samples were cut from the trenches and assayed (Malone, 1962). Jasper (1955 [PE 82-4], 1961) sampled the property during a stripping program carried out in 1954 by Western Alaska Mining Company. The Rhehart-Holoday partnership explored the property from 1965-1972. Bundtzen and others (1998) provide a geologic sketch map of the property as it appeared in 1991.
Indication of production Yes; small
Production notes Most of the following summarizes Bundtzen and others (1998). During the 1880s, Reinhold Separe mined and shipped several tons of high grade mercury ore to a refiner in California. In 1898 Edward Lind, a trader from Kolmakof, mined about five tonnes of ore from the Kolmakof Mine and recovered approximately 150 pounds of mercury. In 1908, Gordon Bettles mined high grade mercury ores from several underground stopes at the Kolmakof deposit and produced an unknown amount of mercury. Sometime prior to 1940, William Holoday opened up the first open cut on the deposit and built a small retort and mill. After World War II, Dean Rhehart constructed a gravity feed mill and produced 136 tonnes of ore averaging about 2.50 percent mercury, from which he recovered about 86 flasks of mercury (Morris Hofseth, oral communication, 1991). The cinnabar concentrates were shipped outside Alaska for refining. The last known production occurred during 1969-70, when the Rhehart-Holoday partnership mined and shipped cinnabar concentrates recovered in a 10-ton-per-day mill. According to Morris Hofseth (oral communication,1991), who worked on the property from 1965 to 1970, the Kolmakof mercury mine has produced about 250 flasks of mercury (about 19,000 pounds) during its long but intermittent operation as a mine.


MRDS Number A013423


Brown, C.M., 1983, Alaska's Kuskokwim River region, a history: U. S. Bureau of Land Management Draft History Summary, 141 p.
Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Gray, J.E., Gent, C.A., Snee, L.W., and Wilson, F.H., 1997, Epithermal mercury-antimony and gold-bearing vein lodes of southwest Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 287-305.
Smith, P.S., and Maddren, A.G., 1915, Quicksilver deposits of the Kuskokwim region, in Brooks, A.H., and others, Mineral resources of Alaska, Report on progress of investigations in 1914: U.S. Geological Survey Bulletin 622-H, p. 272-291.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date 5/3/2003