Bear

Mine, Active

Commodities and mineralogy

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.8612
Longitude -135.0804
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Bear Mine is at an elevation of about 1,500 feet, about 2 miles east-northeast of Pt. Sherman on Lynn Canal and 1 mile southwest of Lions Head Mountain in the Kakuhan Range. It is in the SE1/4 section 4, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

Note: Beginning in the 1990s, this and other old mines and prospects in the vicinity were consolidated by Coeur-Alaska into a single property (Birak, 2006). They have carried out major new drilling and underground exploration that better defines the mineralization, largely blurs the geologic distinction among the old deposits, and extends the ore bodies greatly. They have developed a coherent modern interpretation of the mineralization as a single deposit which Coeur-Alaska intends to mine as a unit. This deposit is described separately in ARDF as the Kensington (Coeur-Alaska) deposit (JU261). For geologic reference purposes and for their historic value, the pre-Coeur-Alaska data for this and the other old mines and prospects that Coeur-Alaska consolidated are retained in ARDF.
The Bear Mine is on a quartz vein in Jualin Diorite. It strikes NW and dips 40-70 NE. It has been traced for 500 feet along strike and 350 feet vertically, and has an average width of 5 to 10 feet (Chris Croff, Placid Oil Co., oral communication, 1987; Redman and others, 1989). The Bear deposit was discovered in 1887 and was mined from 1895 to 1897. Workings include an 1,100-foot crosscut, a 200-foot raise, and 3 levels with 850 feet of drifts. From 1895 to 1897, 800 ounces of gold were recovered from 5,900 tons of ore (Redman and others, 1989).
Geologic map unit (-135.082217936432, 58.8608704720482)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization 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 of deposit 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 and reserves

Workings or exploration The Bear deposit was discovered in 1887 and was mined from 1895 to 1897. Workings include an 1,100-foot crosscut, a 200-foot raise, and 3 levels with 850 feet of drifts.
Indication of production Yes
Production notes From 1895 to 1897, 800 ounces of gold were recovered from 5,900 tons of ore (Redman and others, 1989).

References

MRDS Number A012116

References

Birak, D.J., 2006, Kensington gold project: Unpublished Technical Report for Cour d'Alene Mines, 116 p. (posted on www/.sedar.com, April 20, 2006).
Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Kucinski, R., Porterfield, J., and Croff, C., 1985, Kensington Project summary report - 1985: Unpublished report for Placid Oil Co., 27 p.
Leveille, R.A., 1991, Geology and gold deposits of the Jualin mine area, Berners Bay district, southeastern Alaska: Fairbanks, University of Alaska, M.S. thesis, 200 p.
Miller, L.D., Goldfarb, R.J., Snee, L.W., Gent, C.A., and Kirkham, R.A., 1995, Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay district, southeast Alaska: Economic Geology, v. 90, p. 343-368.
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska ); D.J. Grybeck (Port Ludlow, WA)
Last report date 6/5/2008