Skip to main content

Big Harbor

Mine, Active

Commodities and mineralogy

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale B-3
Latitude 55.37449
Longitude -132.96391
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Big Harbor Mine is on the north side of upper Trocadero Bay, about 0.3 mile north-northeast of the (misplaced) mine symbol on the USGS 1;63,360-scale topographic map. The mine is about 0.5 mile southwest of the center of section 9, T. 75 S., R. 82 E. The location of the mine and its workings are is shown in detail on figure 19 of Maas and others (1995).

Geologic setting

Geologic description The best description of the geology of the deposit at the Big Harbor Mine is in Maas and others (1995), whose report is largely based on a modern interpretation of Pittman's work (1960). The rocks in the vicinity of the deposit were originally felsic to intermediate tuffs, flows and pyroclastics interbedded with argillite, sandstone, and chert. The rocks subsequently underwent greenschist-grade metamorphism to form greenstone, greenschist, and quartz-sericite schist with a strong penetrative fabric. The rocks have been variously dated. Eberlein and others (1983) and Newkirk and others (1993) considered them to be part of of the Descon Formation of Silurian and Ordovician age. They are now generally considered to be part of the Wales Group of Cambrian and older age, mainly on the basis of their penetrative fabric and degree of metamorphism (D.J. Grybeck, unpublished field notes, 1984; Maas and others, 1995; Brew, 1996). Recent detailed geochemical and isotope analyses by Slack and others (2002) confirm that the deposit is of Late Proterozoic or Cambrian age.

The origin of the deposit was variously interpreted prior to the 1950's (Knopf, 1911; Smith, 1914; Chapin, 1918; Twenhofel and others, 1949), but it now is considered to be a volcanogenic massive-sulfide deposit (Newkirk and others, 1993; Maas and others, 1995). It consists of stratiform lenses of pyrite and chalcopyrite with minor sphalerite and magnetite, near a contact between quartz-mica schist and greenstone and greenschist. At the eastern and most extensive workings, a lens of mineralized rock that contains 1.0 to 1.2 percent copper is about 16 to 29 feet thick and extends along strike for about 650 feet. The lens strikes about west and dips about 80N. There are numerous smaller lenses of nearly massive chalcopyrite and pyrite. The lenses are truncated by faults and often pinch and swell along strike. Assays largely reflect the the sulfide content of the masses of ore; some lenses that consist of 1 to 3 feet of chalcopyrite and pyrite contain more than 15% copper. The gold and silver content of the lenses is low. The best gold value in many samples collected by Maas and others (1991, 1995) was 3.5 parts per million (ppm) gold. One high-grade sample contained 1.59 ounces of silver per ton, and 1 sample contained 7.37 percent zinc; most values, however, were much lower. No samples contained more than 871 ppm lead.

The deposit was discovered about 1902 and operated intermittently until 1917 (Knopf, 1911; Brooks, 1912, 1913, 1914,1915; Smith,1914; Chapin, 1916, 1918, 1919; Twenhofel and others, 1949; Roppel, 1991) . The property was acquired by the Northland Development Company in 1908 and they shipped ore in 1912 and 1913. In 1915 or 1916, the mine was taken over by the Southeastern Copper Company, who made a small ore shipment in 1916. No ore has been shipped since. The total production is 136 tons of ore shipped from 1913 to 1916 that contained about 6 to 7 percent copper.

The property was examined by the U.S. Geological Survey in 1944 (Twenhofel and others, 1949) and by the Bureau of Mines in 1958 (Pittman, 1960). The property was restaked by Juan Munoz of Ketchikan in about 1954 and was held by him for at least a decade (D.J. Grybeck, personal interviews with several of the participants, 1984). Eight holes were drilled on the property in 1958, and in the mid-60's the U.S. Bureau of Mines and a private consultant ran several EM and IP lines across the trend of the mineralization; more IP work was done by a private company in 1970. According to Maas and others (1995), the property was examined by Montana Phosphate Products Company in 1957 and 1958, Texas Gulf, Inc. in 1974, and Homestake Mining Company in 1974. The Big Harbor Mine is on land selected by Sealaska Inc. in the mid-70's as part of the Alaska Native Claims Settlement Act, and since then the property has been examined by Anaconda Copper Company in the late 70's, by Exxon Minerals about 1985, and by Cominco Exploration in the early 1990's (Newkirk and others, 1993).

The mine workings are in two mineralized zones about 0.5 mile apart; the workings include four adits, an inclined shaft, several crosscuts and drifts, a 120-foot decline, and numerous pits and trenches. The best description of the workings and their location is in the text and figures of Twenhofel and others (1949), and in the text and on figure 19 of Maas and others (1995).

Pittman (1960) estimated that there is an indicated resource of about 1,450 tons of mineralized rock with 1.0 to 1.2 percent copper for each vertical foot in an orebody that is 16 to 29 feet thick and extends for about 650 feet along strike.

Geologic map unit (-132.965562015397, 55.3741458238775)
Mineral deposit model Probably a Kuroko massive sulfide deposit (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization Volcanogenic massive sulfide copper deposit in Cambrian or older rocks.

Production and reserves

Workings or exploration The mine workings are in two mineralized zones about 0.5 mile apart; the workings include four adits, an inclined shaft, several crosscuts and drifts, a 120-foot decline, and numerous pits and trenches. The best description of the workings and their location is in the text and figures of Twenhofel and others (1949), and in the text and on figure 19 of Maas and others (1995).
Indication of production Yes
Reserve estimates Pittman (1960) estimated that there is an indicated resource of about 1,450 tons of mineralized rock with 1.0 to 1.2 percent copper for each vertical foot in an orebody that is 16 to 29 feet thick and extends for about 650 feet along strike. He did not predict the vertical extent of the ore body.
Production notes The deposit was discovered about 1902 and operated intermittently until 1917 (Knopf, 1911; Brooks, 1912, 1913, 1914, 1915; Smith,1914; Chapin, 1916, 1918, 1919; Twenhofel and others, 1949; Roppel, 1991). The property was acquired by the Northland Development Company in 1908 and they shipped ore in 1912 and 1913. In 1915 or 1916, the mine was taken over by the Southeastern Copper Company, who made a small ore shipment in 1916. No ore has been shipped since. The total production is 136 tons of ore shipped from 1913 to 1916 that contained about 6 to 7 percent copper.
Additional comments This Big Harbor Mine is on or surrounded by land to which the Sealaska Corporation holds the subsurface rights.

References

MRDS Number A010014
References
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Brooks, A.H., 1912, The mining industry in 1911, in Brooks, A.H., and others, Mineral resources of Alaska, report on progress of investigations in 1911: U.S. Geological Survey Bulletin 520-A, p. 17-44.
Brooks, A.H., 1913, The mining industry in 1912: U.S. Geological Survey Bulletin 542-A, p. 18-51.
Brooks, A.H., 1914, Mineral resources of Alaska; report on progress of investigations in 1913: U.S. Geological Survey Bulletin 592, 413 p.
Brooks, A.H., 1915, Mineral resources of Alaska; report on progress of investigations in 1914: U.S. Geological Survey Bulletin 622, 380 p.
Brooks, A.H., 1921, The future of Alaska mining, in Martin, G.C., and others, Mineral resources of Alaska, 1917: U.S. Geological Survey Bulletin 714-A, p. 5-57.
Chapin, Theodore, 1916, Mining developments in southeastern Alaska: U.S. Geological Survey Bulletin 642-B, p. 73-104.
Chapin, Theodore, 1918, Mining developments in the Ketchikan and Wrangell mining districts: U.S. Geological Survey Bulletin 662-B, p. 63-75.
Chapin, Theodore, 1919, A molybdenite lode on Healy River: U.S. Geological Survey Bulletin 692, p. 329.
Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p.
Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p.
Glavinovich, P.S., 1987, Sealaska Corporation Minerals Breifing Book, December 1987: Sealaska Corporation, 40 p. and plates. (Unpublished report held by Sealaska Corporation, Juneau, Alaska).
Hedderly-Smith, D.A., 1991, Report of the 1990 field season-Sealaska Mineral Reconnaissance Project: Sealaska Corporation: Sealaska Corporation, 2 vols., 180 p., 13 plates. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1992, Report of the 1991 field season - Sealaska Mineral Reconnaissance Project: Sealaska Corporation, 2 vols., 225 p. 23 plates. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Knopf, Adolph, 1911, Mining in southeastern Alaska: U.S. Geological Survey Bulletin 480-D, p. 94-102.
Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.
Maas, K.M., Still, J. C., and Bittenbender, P. E., 1992, Mineral investigations in the Ketchikan mining district, Alaska, 1991 - Prince of Wales Island and vicinity: U.S. Bureau of Mines Open-File Report 81-92, 69 p.
Maas, K.M., Still, J. C., Clough, A. H., and Oliver, L. K., 1991, Mineral investigations in the Ketchikan mining district, Alaska, 1990: Southern Prince of Wales Island and vicinity--Preliminary sample location maps and descriptions: U.S. Bureau of Mines Open-File Report 33-91, 139 p.
Newkirk, S.R., Block, W.C., and Anderson, P.W., 1993, Recent developments at the Trocadero Bay, Big Harbor prospect: A Descon-hosted VMS system, southern Prince of Wales Island (abs): Alaska Miners Association, Juneau Branch, Conference Juneau, Abstracts of Professional Papers, p. 35.
Pitman, T.L., 1960, Summary of examination report, Goose claims, Prince of Wales Island, Alaska: U.S. Bureau of Mines summary report, property examination, 10 p. (Unpublished report held by the Bureau of Land Management, Mineral Informaton Center, Juneau, Alaska.)
Roppel, Patricia, 1991, Fortunes from the earth: Manhattan, Kansas, Sunflower University Press, 139 p.
Slack, J.F., Shanks, W.C. III, Karl, S.M., Ridley, W.I., and Bittenbender, P.E., 2002, Geochemical and sulfur isotope compositions of Late Proterezoic and early Paleozoic volcanogenic massive sulfide deposits, Prince of Wales Island and vicinity, southeastern Alaska (abs.): Geological Society of America, Abstracts with Programs, v. 34 (6), p. 113.
Smith, P.S., 1914, Lode mining in the Ketchikan region, Alaska: U.S. Geological Survey Bulletin 592-B, p. 75-94.
Twenhofel, W.S., Reed, J. C., and Gates, G.O., 1949, Some mineral investigations in southeastern Alaska: U.S. Geological Survey Bulletin 963-A, p. 1-45.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004