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Lucky Chance Mine, Chicagof District, Sitka Borough, Alaska, USA

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MAS number: 0021160017.
Location: The Lucky Chance Mine is shown by symbol on the 1:63,360-scale topographic map. It is near the south end of the southern of the Last Chance Lakes and about 0.5 mile south 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 Last Chance Mine was first staked in 1874 and went through a succession of owners to 1904. By 1885, it was developed by a 25-foot shaft and a 30-foot drift (DeArmond, 1997). By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill, a sawmill, and a waterpower generator, and about 1,200 tons of ore had been produced above the main adit which was called the No. 2 tunnel (Becker, 1898; Wright and Wright, 1905; Roehm, 1940). A 3,000- to 4,000-foot tram was built from the mouth of this adit to the mill below and a corduroy road was built to the mine from the head of Silver Bay. The workings include: a 468-foot adit, the No. 2 Tunnel; a 45-foot adit higher on the hillside; a shaft; a glory hole at the top of a stope about 50 feet wide that extends vertically for about 80 feet; and numerous surface trenches. The property was under new ownership in 1940 (Roehm, 1940) but most of the development and production probably took place before the early 1900's. There are no records but there certainly was some production. The deposit at the Last Chance Mine is along a prominent fault zone that strikes about N45W, dips 80-85NE, and cuts graywacke and phyllite (Roehm, 1940). Numerous quartz stringers occur in the fault zone, many at nearly right angles to it, and the stope that was mined coincides with the greatest concentration of these stringers. Many of the quartz stringers persist into phyllite in the hanging wall of the fault. The quartz is generally milky white and often includes partings of the graywacke and phyllite country rock. Minor pyrite and arsenopyrite occur as thin seams and irregular masses up to 0.5 inch thick in the quartz which also carries visible gold. Several samples taken by Roehm (1940) along the hanging wall of the fault/vein contained 0.17 to 1.72 ounces of gold per ton. In the late 1990's, the underground workings were caved but Bittenbender and others (1999) collected several surface samples. Two hand-selected samples from the dump contained 19.3 and 16.9 parts per million (ppm) gold. A sample of concentrates from the mill site contained 26.5 ppm gold, 13 ppm silver, 1,250 ppm lead, and more than 1 percent arsenic.
Workings: The Last Chance Mine was first staked in 1874 and went through a succession of owners to 1904. By 1885, it was developed by a 25-foot shaft and a 30-foot drift (DeArmond, 1997). By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill, a sawmill, and a waterpower generator, and about 1,200 tons of ore had been produced above the main adit which was called the No. 2 Tunnel (Becker, 1898; Wright and Wright, 1905; Roehm, 1940). A 3,000- to 4,000-foot tram was built from the mouth of this adit to the mill below and a corduroy road was built to the mine from the head of Silver Bay. The workings include: a 468-foot adit, the No. 2 tunnel; a 45-foot adit higher on the hillside; a shaft; a glory hole at the top of a stope about 50 feet wide that extends vertically for about 80 feet; and numerous surface trenches. The property was under new ownership in 1940 (Roehm, 1940) but most of the development and production probably took place before the early 1900's.
Age: Cretaceous or younger based on the age of the host rocks.
Production: By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill and about 1,200 tons of ore had been produced above the main adit, the No. 2 tunnel. There are no records but there certainly was some production.
Reserves: None.

Commodities (Major) - Au; (Minor) - Ag, As, Pb
Development Status: Yes; small
Deposit Model: Low-sulfide, gold-quartz vein (Cox and Singer, 1986; model 36a).

Mineral List



4 entries listed. 4 valid minerals.

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References

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.

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