Hirst-Chichagof

Mine, Undetermined

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; pyrite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SI
Quadrangle map, 1:63,360-scale C-7
Latitude 57.6848
Longitude -136.1038
Nearby scientific data Find additional scientific data near this location
Location and accuracy The well-known Hirst-Chichagof Mine is at the head of Kimshan Cove. Its patented and unpatented claims stretch southeast from near sea level for about a mile along the northeast flank of Doolth Mountain. For this record, the site is plotted at an elevation of 100 feet, 0.4 mile north of the center of sec. 25, T. 48 S., R. 57 E. It is location P-60 of Bittenbender and others (1999), location 27 of Cobb (1972, 1978), and MAS no. 0021140003 (U.S. Bureau of Land Management, 2002). The location is accurate.

Geologic setting

Geologic description

The most productive mines and most of the significant prospects on western Chichagof Island are centered on Doolth Mountain in an approximately 4-square-mile area between the head of Klag Bay and south of Kimshan Cove (Reed and Coats, 1941; Bittenbender and others, 1999). The area is underlain by the Cretaceous Sitka Graywacke which consists of massive, thick-bedded, and slaty graywacke, locally interbedded with lenticular layers of recrystallized basalt ('greenstone') (Johnson and Karl, 1985). The strata generally strike northwest and dip steeply southwest. They are intruded by felsic and mafic dikes, but no granitic plutons are exposed in the area. All of the rocks are regionally metamorphosed to prehnite-pumpellyite grade, and some of the dikes are silicified near the orebodies (Reed and Coats, 1941).
The principal structures in the area are numerous northwest-striking, steeply-dipping faults. Two of them, the Hirst and Chichagof faults, and splays ('splits') from them, localized the principal orebodies, particularly where variations in the intersections of faults and bedding created potential openings that allowed increased fluid migration and mineralization (Bittenbender and others, 1999).
The deposits are auriferous quartz veins containing pyrite, arsenopyrite, galena, sphalerite, chalcopyrite, and native gold, most of which is free-milling. The quartz is accompanied by a little calcite, and a little gold occurs in the wallrocks of the veins. The productive veins commonly have a ribbon structure, characterized by graphitic partings, and commonly are accompanied by graphitic gouge. Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler and others, 1995; Goldfarb, 1997; Goldfarb and others, 1997).
The first claim on what was to become the Hirst-Chichagof Mine was located in 1905, and from 1922 to 1933, the mine produced 131,000 ounces of gold and 33,000 ounces of silver from more than 140,000 tons of ore (Reed and Coats, 1941; Bittenbender and others, 1999). The mine closed in 1943. From 1950 to 1954, 124 ounces of gold were recovered from a mill cleanup and from mine tailings (Still and Weir, 1981). Still and Weir report that the mine explored the Hirst Fault for about a mile along strike, and up to 2,000 feet vertically. Mining reached a depth of 1,800 feet below sea level. The workings, almost all of which are inaccessible, included an adit with four levels totaling 6,950 feet, and two shafts.
The U.S. Bureau of Mines (Still and Weir, 1981) estimated the remaining resources on the basis of examinations in 1978 and 1979 of surface and accessible underground workings. Their estimates include 30,000 tons of material with an average grade of 1.0 ounce of gold per ton; 70,000 tons with an average grade of 0.25 ounce of gold per ton; and 70,000 tons of tailings with an average grade of 0.14 ounce of gold per ton.
From 1981 to 1983, private interests explored the workings and evaluated the tailings. In 1986, other interests drove a 160-foot crosscut and established a drill station. By 1988, they had rehabilitated some underground workings and completed about 3,215 feet of core drilling to test the possible extension of the Kay oreshoot below previously developed mine levels. The work did not intersect ore. Nevertheless, they estimated the resources remaining in the ore shoot as 30,380 tons of probable, possible, and inferred ore with an average grade of 1.0 ounce per ton.
Geologic map unit (-136.105626619582, 57.6844274610098)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Isotopic studies indicate that the gold-quartz veins in coastal southern and southeastern Alaska are Eocene, about 50 Ma in age (Haeussler and others, 1995; Goldfarb, 1997; Goldfarb and others, 1997).
Alteration of deposit Dikes are silicified near orebodies.

Production and reserves

Workings or exploration Still and Weir (1981) report that the Hirst-Chichagof Mine explored the Hirst Fault for about a mile along strike, and up to 2,000 feet vertically. Mining reached a depth of 1,800 feet below sea level. The workings, almost all of which are inaccessible, included an adit with four levels totaling 6,950 feet, and two shafts. From 1981 to 1983, private interests explored the workings and evaluated the tailings. In 1986, other interests drove a 160-foot crosscut and established a drill station. By 1988, they had rehabilitated some underground workings and completed about 3,215 feet of core drilling to test the possible extension of the Kay oreshoot below previously developed mine levels. The work did not intersect ore.
Indication of production Yes; medium
Reserve estimates
The U.S. Bureau of Mines (Still and Weir, 1981) estimated the remaining resources on the basis of examinations in 1978 and 1979 of surface and accessible underground workings. Their resource estimates include 30,000 tons of material with an average grade of 1.0 ounce of gold per ton; 70,000 tons with an average from of 0.25 ounce of gold per ton; and 70,000 tons of tailings with an average grade of 0.14 ounce of gold per ton.
From 1981 to 1983, private interests explored the workings and evaluated the tailings. In 1986, other interests drove a 160-foot crosscut and established a drill station. By 1988, they had rehabilitated some underground workings and completed about 3,215 feet of core drilling to test the possible extension of the Kay oreshoot below previously developed mine levels. The work did not intersect ore. Nevertheless, they estimated the resources remaining in the Kay ore shoot as 30,380 tons of probable, possible, and inferred ore with an average grade of 1.0 ounce per ton.
Production notes From 1922 to 1933 the Hirst-Chichagof Mine produced 131,000 ounces of gold and 33,000 ounces of silver from more than 140,000 tons of ore (Reed and Coats, 1941; Bittenbender and others, 1999). From 1950 to 1954, 124 ounces of gold were recovered from a mill cleanup and from mine tailings (Still and Weir, 1981).

Additional comments

The entire Chichagof Mining District is in West Chichagof-Yakobi Wilderness although there are patented claim blocks within the wilderness such as those that cover this mine.

References

MRDS Number A010687; A013265; A013266

References

Bittenbender, P., Still, J.C., Maas, K., and McDonald, M., Jr., 1999, Mineral resources of the Chichagof and Baranof Islands area, southeast Alaska: Bureau of Land Management, BLM-Alaska Technical Report 19, 222 p.
Dadoly, J.P., 1987, Gold mineralization in a regional metamorphic terrane: A wall-rock alteration study of the Chichagof and Hirst-Chichagof gold mines, southeast Alaska: Unpublished M. S. thesis, South Dakota School of Mines, Rapid City, SD, 125 p.
Fiedler, H.L., 1941, Report to the Commissioner of Mines on the inspection of the Hirst-Chichagof Mining Company, Kimshan Cove, Alaska: Unpublished report, 16 p. (Report held by the Mineral Information Center, Bureau of Land Management, Juneau, Alaska.)
Golden Sitka Resources Inc., 1987, Prospectus, 36 p. (Report held by the Mineral Information Center, Bureau of Land Management, Juneau, Alaska.)
Goldfarb, R J., 1997, Metallogenic evolution of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 4-34.
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.
Haeussler, P J., Bradley, D., Goldfarb, R., Snee, L., and Taylor, C., 1995, Link between ridge subduction and gold mineralization in southern Alaska: Geology, v. 23, no. 11, p. 995-998.
Humphrey, H.B., 1936, Hirst-Chichagof Mine: Unpublished U. S. Bureau of Mines report, 7 p. (Report held by the Mineral Information Center, Bureau of Land Management, Juneau, Alaska.)
Humphrey, H.B., 1938, Improvements at Hirst-Chichagof Mine, Kimshan Cove, Alaska: Unpublished U. S. Bureau of Mines report, 3 p., available from the Mineral Information Center, Bureau of Land Management, Juneau, AK.
Kazee, H M., 1941, Hirst-Chichagof Mining Company: Unpublished report, 10 p. (Report held by the Mineral Information Center, Bureau of Land Management, Juneau, Alaska.)
Metz, P.A., 1978, Chichagof and Hirst-Chichagof Mines, Chichagof Mining District, Alaska: U. S. Bureau of Mines Summary Report, 19 p.
Northern Miner, 1988, Golden Sitka busy at Chichagof: Northern Miner, v. 74, no. 24, p. 6.
Reed, J.C., 1939, Preliminary report on the ore deposits of the Chichagof Mining District, Alaska: American Institute of Mining & Metallurgy, Engineering Technical Publication 1051, 20 p.
Thorne, R.L., 1967, Chichagof Mining District, Sitka quadrangle, southeastern Alaska: Unpublished U. S. Bureau of Mines Situation report, 5 p.
U.S. Bureau of Land Management, 2002, Alaska mineral locations database report (Sitka quadrangle), July 2, 2002, 205 p. [http://imcg.wr.usgs.gov/dem.html]
Reporters H.C. Berg (U.S. Geological Survey)
Last report date 10/16/2004