Location: The Comet Mine is at an elevation of about 2,300 feet, about 3 miles east of Pt. Sherman on Lynn Canal and 1.5 miles south-southwest of Lions Head Mountain in the Kakuhan Range. The mine is marked on the Juneau D-4 topographic map. It is in the NE1/4 section 9, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.
Geology: The deposit at the Comet Mine consists of 2 principal quartz veins about 50 ft apart that strike north and dip 70 E. The largest vein is 300-500 ft long; it averages 2 to 3 feet wide at the surface and up to 9 feet thick in underground exposures. The vein is truncated to the north by a large, left-lateral fault; to the south it crosses a diorite-phyllite contact, where it splits and ends. The veins carry pyrite, chalcopyrite, galena and free gold (Redman and others, 1989). The Comet Mine is the largest gold producer in the Berners Bay region producing 22,485 ounces of gold from 51,463 tons of ore between 1894 and 1900. The deposit was discovered in the 1880's and tunneling began in 1891. A 20-stamp mill was in place by 1892 and production began in 1894. The mine has 9,000 feet of workings on 9 levels, 5 adits, and 1 open stope. Placid Oil Co. drilled 2 core holes in 1981 (Kucinski and others, 1985). The property is currently (2001) controlled by Coeur Alaska. The Comet mine is in the Berners Bay district at the north end of the Juneau Gold Belt. The district is characterized by a series of structurally-controlled, mesothermal, gold-bearing quartz veins. Most of the veins are in Early Cretaceous (105 Ma) Jualin Diorite, which intrudes Upper Triassic metabasalt. The Jualin Diorite is generally massive, jointed, blocky, quartz monzonite to quartz monzodiorite. Gold occurs in low-sulfide, quartz-carbonate veins that contain pyrite and tellurides; the veins are marked by distinctive ankeritic alteration zones. There are both extensional and shear veins that generally strike north to northwest and dip east. Discrete vein systems are defined by one or more through-going quartz veins, many of which are in shear zones. Levielle (1991) and Knopf (1911) describe other gangue minerals near vein margins including albite, chlorite, muscovite, and lesser tourmaline, rutile, and apatite. Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization, sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991). Pyrite is the most abundant sulfide mineral, with lesser amounts of chalcopyrite, galena, sphalerite, arsenopyrite, and tetrahedrite. Gold occurs in the native state, in pyrite, and in various telluride minerals such as calaverite, hessite, and petzite (Leveille, 1991; Redman and others, 1989). The vein paragenesis consists of early quartz, carbonates, albite and pyrite, followed by deposition of base and precious metals. Gold, galena and the tellurides were the last to be deposited (Leveille, 1991). The age of hydrothermal muscovite from veins at Kensington Mine (JU029) varies from 53.4 Ma to 56.5 Ma (Miller and others, 1994). This coincides with the 55 Ma age of the other mesothermal gold vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Workings: The Comet deposit was discovered in the 1880's and tunneling began in 1891. A 20-stamp mill was in place by 1892 and production began in 1894. The mine has 9,000 feet of workings on 9 levels, 5 adits and 1 open stope. Placid Oil Co. drilled several core holes in 1981. The property is currently (2001) controlled by Coeur Alaska.
Age: The age of mineralization in the Berners Bay district is about 55 Ma, the same as the other mesothermal gold-quartz-vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Alteration: Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite alteration (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization and sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991).
Production: The Comet Mine is the largest gold producer in the Berners Bay region producing 22,485 ounces of gold from 51,463 tons of ore between 1894 and 1900. The deposit was discovered in the 1880's and tunneling began in 1891. A 20-stamp mill was in place by 1892 and production began in 1894.

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

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Mineral List

ⓘ var. Iron-bearing Dolomite

8 valid minerals.