Alaska Treasure

Mine, Inactive

Alternative names

Nevada Creek

Commodities and mineralogy

Main commodities Ag; Au; Pb; Zn
Other commodities Cu
Ore minerals chalcopyrite; galena; pyrite; pyrrhotite; sphalerite; tetrahedrite
Gangue minerals calcite; dolomite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale A-1
Latitude 58.2262
Longitude -134.3148
Nearby scientific data Find additional scientific data near this location
Location and accuracy This mine is at an elevation of approximately 300 feet on Nevada Creek on southeastern Douglas Island. It is in the SE1/4 section 17, T. 42 S., R. 68 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Alaska Treasure Mine was discovered in 1884. No development work was done until 1904-1905 when a road was constructed from the beach to the mine site (Redman and others, 1989). A 20-stamp mill was installed in 1906 and development continued intermittently until 1916. Approximately 800 tons of ore was mined but detailed production records are not available. The mine was explored by BP Minerals in the late 1980s and by Hecla Mining Company in 1990 and 1991 (Bundtzen and others, 1991; Swainbank and others, 1991). The main workings are a 3,350-foot adit with 760 feet of drifts. Other workings include the 657-foot Hudson Tunnel with 280 feet of drifts, 2 other adits, and 3 shafts. There is a total of 5,509 feet of underground workings.
The host rocks at the mine are quartz-feldspar-sericite phyllite intercalated with volcanic metaconglomerate and pale green, chlorite phyllite (Wells and others, 1986). The felsic phyllite is locally silicified and sericitized. It contains up to 5 percent disseminated pyrite and thin concordant bands of pyrite, galena, chalcopyrite, sphalerite, pyrrhotite, and tetrahedrite in a gangue of quartz and dolomite. The bands are up to 2 inches thick and can be traced for nearly 300 feet. Quartz veins containing up to 30 percent pyrite, galena, chalcopyrite and sphalerite also occur at the mine, but they are distant from the sulfide-rich zones in the felsic phyllite. U.S. Bureau of Mines samples contained up to 75.4 ppm gold, 47.0 ppm silver, 3.7 percent lead, and 5.1 percent zinc (Redman and others, 1989). A 275-pound metallurgical sample collected by the U.S. Bureau of Mines assayed 3.9 ppm gold; a cyanide-amenability test recovered 77.6 percent of the gold. The Bureau has calculated an indicated resource of 240,000 tons of ore with 0.1 ounce of gold per ton, and an inferred resource of 5.6 million tons of ore with 0.05 ounce of gold per ton (Redman and others, 1989). The deposit is similar to the Yakima (JU207), Red Diamond (JU232), Mammoth (JU229), and Homestake prospects (JU231), which Newberry and others (1997) interpret as Cretaceous volcanogenic massive sulfide deposits.
Southeastern Douglas Island is underlain mainly by Upper Jurassic to mid-Cretaceous, marine argillite and graywacke, interbedded with basaltic volcanic and volcaniclastic rocks (Brew and Ford, 1985). The strata are regionally metamorphosed to prehnite-pumpellyite or greenschist grade.
Geologic map unit (-134.316564329774, 58.2258706063064)
Mineral deposit model Metamorphosed Kuroko massive sulfide deposit (Cox and Singer, 1986; model 28a)
Mineral deposit model number 28a
Age of mineralization Newberry and others (1997) have interpreted this deposit as a Cretaceous volcanogenic massive sulfide deposit.
Alteration of deposit Sericitization, silicification, and pyritization.

Production and reserves

Workings or exploration The Alaska Treasure Mine was discovered in 1884. No development work was done until 1904-1905 when a road was constructed from the beach to the mine site (Redman and others, 1989). A 20-stamp mill was installed in 1906 and development continued intermittently until 1916. The mine was explored by BP Minerals in the late 1980s and by Hecla Mining Company in 1990 and 1991(Bundtzen and others, 1991; Swainbank and others, 1991). The main workings at the mine are a 3,350-foot adit with 760 feet of drifts. Other workings include the 657-foot Hudson Tunnel with 280 feet of drifts, 2 other adits, and 3 shafts. There is a total of 5,509 feet of underground workings.
Indication of production Yes; small
Reserve estimates The U.S. Bureau of Mines has calculated an indicated resource of 240,000 tons of ore with 0.1 ounce of gold per ton, and an inferred resource of 5.6 million tons of ore with 0.05 ounce of gold per ton (Redman and others, 1989).
Production notes Approximately 800 tons of ore was mined but production records are not available.

References

MRDS Number A012026

References

Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 12/15/2001