Fidalgo Mining Co. (Blackney Prospect)

Mine, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au
Ore minerals chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale CV
Quadrangle map, 1:63,360-scale D-7
Latitude 60.7951
Longitude -146.2947
Nearby scientific data Find additional scientific data near this location
Location and accuracy This mine is at an elevation of about 500 feet on the south side of Port Fidalgo, about 1.5 miles northwest of the head of Matthews Bay. It is in the SE1/4 sec. 28, T. 12 S., R. 6 W., of the Copper River Meridian. The location is accurate to within 500 ft. This mine is shown as site #21 in Cobb (1972: MF-392) and C-63 in Jansons and others (1984).

Geologic setting

Geologic description

Most of the ore mined from this deposit was from two lens-shaped bodies of massive sulfides. The ore bodies were localized in a shear zone in interbedded volcanic and sedimentary rocks of the Tertiary Orca Group (Nelson and others, 1985; Moffit and Fellows, 1950). Sulfide minerals include chalcopyrite, pyrite, and pyrrhotite. Underground study by Jansons and others (1984) reported three main shear zones up to 30 feet wide and traceable for 4000 feet parallel to bedding.
Most of the mining activity took place in 1913. The average copper grade was 13 percent. The mine continued to be active until 1920 (Moffit and Fellows, 1950). Workings included four adits having the following lengths: 1200 ft., 735 ft., 350 ft., and 175 ft. The following assays are reported by Jansons and others (1984). Four chip samples from the 735-foot-long adit contained from 175 parts per million (ppm) to 0.23 percent Cu; nine chip samples across the main shear zone in the 1200-foot-long adit contained 0.12 percent to 1.25 percent copper; fifteen chip samples from the rest of the adit contained 9 ppm to 0.29 percent Cu; and three chip samples from the 175-foot-long adit contained 300 ppm to 0.73 percent Cu; three chip samples from the 350-foot-long adit contained 0.17 percent to 0.73 percent Cu. Grab samples from the dump contained 1 percent to 6.3 percent Cu. Industry evaluation of the property was undertaken in 1986 (B. Ellis, personal communication, 2000).
A 2014 grab sample contained 0.117 ppm Au, 3.96 ppm Ag, 0.819 percent Cu, and 0.236 percent Zn (Angel, 2014).
Geologic map unit (-146.296680049358, 60.7945594593841)
Mineral deposit model Besshi massive sulfide (Cox and Singer, 1986; model 24b)
Mineral deposit model number 24b
Age of mineralization Tertiary based on the age of the host rocks.
Alteration of deposit Oxidation of copper minerals (Angel, 2014).

Production and reserves

Workings or exploration
Most of the mining activity took place in 1913. The average copper grade was 13 percent. The mine continued to be active until 1920 (Moffit and Fellows, 1950). Workings included four adits having the following lengths: 1200 ft., 735 ft., 350 ft., and 175 ft. The following assays are reported by Jansons and others (1984). Four chip samples from the 735-foot-long adit contained from 175 parts per million (ppm) to 0.23 percent Cu; nine chip samples across the main shear zone in the 1200-foot-long adit contained 0.12 percent to 1.25 percent copper; fifteen chip samples from the rest of the adit contained 9 ppm to 0.29 percent Cu; and three chip samples from the 175-foot-long adit contained 300 ppm to 0.73 percent Cu; three chip samples from the 350-foot-long adit contained 0.17 percent to 0.73 percent Cu. Grab samples from the dump contained 1 percent to 6.3 percent Cu. Industry evaluation of the property was undertaken in 1986 (B. Ellis, personal communication, 2000).
Field work including sampling was performed in 2014. A 2014 grab sample contained 0.117 ppm Au, 3.96 ppm Ag, 0.819 percent Cu, and 0.236 percent Zn (Angel, 2014).
Indication of production Yes; small
Reserve estimates Inferred reserves: 45,500 tons at 0.3 percent Cu (Jansons and others, 1984).
Production notes 360,376 lbs. Cu and 12 oz Ag were recovered from 2,747 tons ore, which also contained as much as 0.05 oz. Au/ton.

Additional comments

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 10307364

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 9/9/2014