Liberty Mine, Chichagof District, Sitka Borough, Alaska, USA
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Geology: The host rock at the Liberty Mine is part of the Jurassic and Cretaceous, Sitka Graywacke which consists mainly of graywacke and argillite (Loney and others, 1975). The mine was first mentioned by Becker (1898) when the property was in operation. He described the deposit as a series of imbricate quartz lenses up to 7 feet thick, along a fault. The vein contained pyrite, chalcopyrite, and arsenopyrite. A mill recovered about $2.50 in gold per ton of feed stock and about half of the gold was probably passed into the tailings. Some mill test recovered as much as $5 per ton, i.e., the ore contained up to about 0.5 ounce of gold per ton. The amount of gold that was produced was not given. There is no indication of any significant amount of work on the property after 1905 (Wright and Wright, 1905; Wright, 1907; Knopf, 1912). The deposit was mapped by Bittenbender and others (1999) who located two adits, one 30 feet long and the other 300 feet long. In the longer adit, discontinuous quartz lenses, often brecciated, are exposed along a fault zone for about 100 feet. The quartz lenses are up to 5 feet thick. The quartz contains minor sulfides, mainly pyrite. The best sample they collected contained 60 parts per billion gold, across 3 feet. Samples contained up to 398 parts per million (ppm) arsenic and two samples contained more than 2 ppm mercury. The same vein structure is exposed in the shorter and higher adit.
Workings: The property was active before 1900, but probably not in any substantial way since.
Age: Jurassic or younger based on the age of the host rock.
Production: Becker (1898) implies that some gold was produced.
Commodities (Major) - Au; (Minor) - As, Cu, Hg
Development Status: Yes; small
Deposit Model: Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
3 entries listed. 3 valid minerals.
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Becker, G.F., 1898, Reconnaissance of some gold fields of southern Alaska, with some notes on general geology: U.S. Geological Survey 18th annual report, Part 3, p. 7-86. Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p. Knopf, Adolph, 1912, The Sitka mining district, Alaska: U.S. Geological Survey Bulletin 504, 32 p. Loney, R.A., Brew, D.A., Muffler, L.J.P., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p. U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html] Wright, C.W., 1907, Lode mining in southeastern Alaska: U.S. Geological Survey Bulletin 314, p. 47-72. Wright, F.E., and Wright, C.W., 1905, Economic developments in southeastern Alaska: U.S. Geological Survey Bulletin 259, p. 47-68.