Reynolds-Alaska Development Co.

Mine, Inactive

Commodities and mineralogy

Main commodities Cu; Zn
Other commodities Ag
Ore minerals chalcopyrite; pyrrhotite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-8
Latitude 60.833
Longitude -146.628
Nearby scientific data Find additional scientific data near this location
Location and accuracy The map site of this mine is at the position of the main tunnel, which is at sea level on the east side of Boulder Bay. The site is in the S1/2 sec. 27, T. 11 S., R 8 W., of the Copper River Meridian. The location is accurate to within 1000 ft. This mine is shown as #7 in Cobb (1972: MF-392) and as C-87 in Jansons and others (1984).

Geologic setting

Geologic description

The country rocks at this mine are mafic volcanic rocks and sedimentary rocks of the Tertiary Orca Group (Nelson and others, 1985). The deposit consists of massive sulfide lenses, and sulfide veins, disseminations, and thin selvages in shear zones (Jansons and others, 1984). The sulfide minerals are chalcopyrite, pyrrhotite, and sphalerite. The ore minerals are restricted to north-trending and steeply-dipping shears at the contact of volcanic and sedimentary rock.
Grant and Higgins (1909) report that some large beach boulders were shipped as ore. Chip samples collected in the 1980s contained 0.6 to 1.7 percent Cu, 225 parts per million (ppm) to 0.6 percent Zn, and 2.4 ppm to 8.9 ppm Ag; grab samples contained 60 ppm to 6 percent Cu, 67 ppm to 1.7 percent Zn, and 1.1 ppm to 13 ppm Ag (Jansons and others, 1984).
Three grab samples were collected in 2014 for analyses. Sample 1 contained 0.93 ppm Au, 10.9 ppm Ag, 1.67 percent Cu, and 0.1520 percent Zn. Sample 2 contained 0.396 ppm Au, 1.01 ppm Ag, 0.13 percent Cu, and 0.506 percent Zn. Sample 3 contained 0.077 ppm Au, 1.24 ppm Ag, 0.691 percent Cu, and 0.164 percent Zn (Angel, 2014).
Geologic map unit (-146.630007835286, 60.8824550432549)
Mineral deposit model Cyprus massive sulfide (Cox and Singer, 1986; model 24a)
Mineral deposit model number 24a
Age of mineralization Probably Tertiary based on the age of the host rocks (Nelson and others, 1985).
Alteration of deposit Oxidation of copper minerals (Angel, 2014).

Production and reserves

Workings or exploration
The mine was developed in the early 1900s by 2100 feet of drifts (main tunnel), numerous crosscuts, winzes and raises, and at least 500 ft. of additional tunnels (Capps and Johnson, 1915). One 200 ft. tunnel was caved by the early 1980s (Jansons and others, 1984). Grant and Higgins (1909) report that some large beach boulders were shipped as ore. Chip samples collected in the 1980s contained 0.6 to 1.7 percent Cu, 225 parts per million (ppm) to 0.6 percent Zn, and 2.4 ppm to 8.9 ppm Ag; grab samples contained 60 ppm to 6 percent Cu, 67 ppm to 1.7 percent Zn, and 1.1 ppm to 13 ppm Ag (Jansons and others, 1984).
Field work including sampling was performed in 2014. Three grab samples were collected in 2014 for analyses. Sample 1 contained 0.93 ppm Au, 10.9 ppm Ag, 1.67 percent Cu, and 0.1520 percent Zn. Sample 2 contained 0.396 ppm Au, 1.01 ppm Ag, 0.13 percent Cu, and 0.506 percent Zn. Sample 3 contained 0.077 ppm Au, 1.24 ppm Ag, 0.691 percent Cu, and 0.164 percent Zn (Angel, 2014).
Indication of production Yes; small
Reserve estimates Inferred reserves of 600 tons at 1.37 percent Cu, 0.28 percent Zn, and 6.67 ppm Ag (Jansons and others, 1984).
Production notes 215,000 pounds of copper were recovered from 2,850 tons of ore (Jansons and others, 1984).

Additional comments

Nelson and others (1985) interpret the country rocks as accreted ocean crust. Crowe and others (1992; 1993) and Sainsbury (1993) discuss the genesis of the volcanogenic massive sulfide deposits in this area.
Chugach Alaska Corporation, Anchorage, Alaska has control of these lands.

References

MRDS Number A010438

References

Angel, A.K., 2014 Mineral Assessment of Chugach Alaska Lands, Unpublished Report, 21p. (Report held by Chugach Alaska Corporation, Anchorage, Alaska).
Sainsbury, C.L., 1993, Geology and geochemistry of volcanogenic massive sulfide deposits and related igneous rocks, Prince William Sound, south-central Alaska, A discussion: Economic Geology, v. 88, p. 1284-1285.
Reporters S.W. Nelson, Anchorage, AK; A.K. Angel (Alaska Earth Sciences, Inc.)
Last report date 1/14/2015