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Cymru Mine, Miller Lake (Mineral Lake), Prince of Wales Island, Ketchikan District, Prince of Wales-Outer Ketchikan Borough, Alaska, USA

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Location: The Cymru Mine is just north of the southeast end of Miller Lake (called Mineral Lake in early reports). It is about 0.5 mile west-southwest of the center of section 5, T. 78 S., R. 88 E. Maas and others (1995) provide a detailed map of the surface and underground workings.
Geology: The Cymru Mine was found in 1899 and by 1900, a 30-foot tunnel had been driven on the deposit (Brooks, 1902; Wright, 1908; Wright and Wright, 1908; Chapin, 1916; Bufvers, 1967; Roppel, 1991; Maas and others, 1991, 1995). By 1906, a substantial camp had been built at the property and the first ore was shipped via a 4,200-foot tram to a dock on Clarno Cove. A fire destroyed most of the facilities in 1907; the plant was quickly rebuilt but the property soon had financial difficulties. A new company was established to operate the property in 1914; considerable work was done, but only a small amount of ore was shipped in 1916. There has been no production since then and by 1928, the buildings and tramway had largely been overgrown or had collapsed. The deposit was developed by two short adits, several shafts, and about 400 feet of underground workings. They connected to several stopes that extended from the surface to the deepest workings at a depth of about 30 feet. The rocks in the vicinity of the mine are Late Proterozoic or Cambrian marble and greenschist of the Wales Group (Eberlein and others, 1983; Brew, 1996). The deposit at the mine is usually described as a conformable quartz-calcite vein up to 6 feet thick in marble interbedded with calcareous greenschist (Wright and Wright, 1908; Maas and others, 1991, 1995). More likely it is a folded, stratiform layer in the host rocks (D.J. Grybeck personal observation, 1983). The mineralization consists of disseminations and sulfide-rich bands of chalcopyrite and pyrite. The deposit can be traced for about 1,200 feet on the surface and in underground workings. The deposit and the host rocks strike about N55W and dip 70SW. Maas and others (1991) collected 26 samples, many underground in the old workings. The best values were from a portion of the ore body about 4.3 feet thick that averaged 3.98 percent copper. The silver content varies with the copper content; the highest silver value was 9.06 ounces per ton. The highest gold value was 0.21 parts per million (ppm), the highest zinc value was 436 ppm, and the highest lead value was 45 ppm. The Cymru Mine produced 141,700 pounds of copper, 1,417 ounces of silver, and 28.34 ounces of gold in 1916, and 9,570 pounds of copper and 69 ounces of silver in 1915 (Maas and others, 1991,1995).
Workings: The Cymru Mine was found in 1899 and by 1900, a 30-foot tunnel had been driven on the deposit (Brooks, 1902; Wright, 1908; Wright and Wright, 1908; Chapin, 1916; Bufvers, 1967; Roppel, 1991; Maas and others, 1991, 1995). By 1906, a substantial camp had been built at the property and the first ore was shipped via a 4,200-foot tram to a dock on Clarno Cove. A fire destroyed most of the facilities in 1907; the plant was quickly rebuilt, but the property soon had financial difficulties. A new company was established to operate the property in 1914; considerable work was done, but only a small amount of ore was shipped in 1916. There has been no production since then and by 1928, the buildings and tramway had largely been overgrown or had collapsed. The deposit was developed by two short adits, several shafts, and about 400 feet of underground workings. They connected to several stopes that extended from the surface to the deepest workings at a depth of about 30 feet.
Age: Unclear whether this is an epigenetic deposit or a folded, copper-rich, stratiform layer in the Late Proterozoic or Cambrian host rocks.
Production: The Cymru Mine produced 141,700 pounds of copper, 1,417 ounces of silver, and 28.34 ounces of gold in 1916, and 9,570 pounds of copper and 69 ounces of silver in 1915 (Maas and others, 1991, 1995).

Commodities (Major) - Ag, Au, Cu
Deposit Model: A layer or vein of sulfide-bearing calcite and quartz in marble and greenschist.

Mineral List



4 entries listed. 4 valid minerals.

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References

Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p. Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000. Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p. Brooks, A.H., 1915, Mineral resources of Alaska; report on progress of investigations in 1914: U.S. Geological Survey Bulletin 622, 380 p. Brooks, A.H., 1921, The future of Alaska mining, in Martin, G.C., and others, Mineral resources of Alaska, 1917: U.S. Geological Survey Bulletin 714-A, p. 5-57. Bufvers, John, 1967, History of mines and prospects, Ketchikan district, prior to 1952: Alaska Division of Mines and Minerals Special Report 1, 32 p. Chapin, Theodore, 1916, Mining developments in southeastern Alaska: U.S. Geological Survey Bulletin 642-B, p. 73-104. Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p. Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p. Maas, K.M., Still, J. C., Clough, A. H., and Oliver, L. K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: Southern Prince of Wales Island and vicinity--Preliminary sample location maps and descriptions: U.S. Bureau of Mines Open-File Report 33-91, 139 p. Roppel, Patricia, 1991, Fortunes from the earth: Manhattan, Kansas, Sunflower University Press, 139 p. Wright, C.W., 1907, Lode mining in southeastern Alaska: U.S. Geological Survey Bulletin 314, p. 47-72. Wright, C.W., 1908, Lode mining in southeastern Alaska, 1907: U.S. Geological Survey Bulletin 345-B, p. 78-97. Wright, C.W., 1909, Mining in southeastern Alaska: U.S. Geological Survey Bulletin 379-B, p. 67-86. Wright, F.E., and Wright, C.W., 1908, The Ketchikan and Wrangell mining districts, Alaska: U.S. Geological Survey Bulletin 347, 210 p.

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