Free Gold Occurrences, Chicagof District, Sitka Borough, Alaska, USA
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Location: The Free Gold prospect is shown by symbol on the 1:63,360-scale topographic map. It is about 0.6 mile east-northeast of Pinta Lake and about 0.4 mile north of the center of section 5, T. 57 S., R. 66 E.
Geology: This deposit is one of many of similar deposits (PA002 to PA018) scattered over an area of about 6 square miles at the head of Silver Bay (Bittenbender and others, 1999). The deposits are gold-quartz veins with sparse sulfides, usually only pyrite and arsenopyrite. Samples that have been analyzed with modern methods usually show anomalous arsenic even if arsenopyrite is not identified in the rocks, and several parts per million mercury. The veins are often parallel to the bedding of the host rock which is graywacke and argillite of the Sitka Graywacke of Cretaceous age (Loney and others, 1975). Many of the so-called veins in the early literature are actually fault zones with lenses of quartz or concentrations of quartz stringers along the fault zone. Prospecting began in the area in 1871. The Stewart Mine (PA012) was located in 1872 and it was the first lode-gold mine in Alaska. The Silver Bay area has been prospected intermittently to the present but the veins are relatively small and most are low grade. The area has produced relatively little gold, many of the properties have not been active since before 1900, and there has been no production since the early 1940's. The Free gold prospect was staked in 1876 and an arrastre and mine buildings were built in 1879 (Becker, 1898); Wright and Wright (1905) and Knopf (1912) described the prospect as active but there apparently has been no later work on the prospect. A map by the Edgecumbe Exploration Company shows an adit in the vicinity, but Bittenbender and others (2002) who cite the map could not find the adit. They did find quartz veins in the area that cut massive graywacke. Samples contained low precious metal values; none of the quartz had visible sulfides. But a piece of float collected near the northwest side of the northern of the Lucky Chance Lakes contained 1,180 parts per billion gold.
Workings: There was considerable work on this prospect prior to 1912 including the construction of an arrastre and several mine buildings. There is no indication of later work other than sampling by government geologists in the late 1990's.
Age: Cretaceous or younger based on the age of the host rock.
Commodities (Major) - Au
Development Status: None
Deposit Model: Low-sulfide, gold-quartz vein (Cox and Singer, 1986; model 36a).
1 entry listed. 1 valid mineral.
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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. Cobb, E.H., 1972, Metallic mineral resources map of the Port Alexander quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-464, 1 sheet, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Port Alexander quadrangle: U.S. Geological Survey Open-File Report 78-787, 33 p. DeArmond, R.N., 1997, Haleys and Silver Bay, in Around and About Alaska: Sitka Sentinel, series of 29 Articles, April to October, 1997. 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. B., and Pomeroy, J.S., 1975, Reconnaissance geology of Chichagof, Baranof, and Kruzof Islands, southeastern Alaska: U.S. Geological Survey Professional Paper 792, 105 p. Wright, F.E., and Wright, C.W., 1905, Economic developments in southeastern Alaska: U.S. Geological Survey Bulletin 259, p. 47-68.