It

Mine, Active

Alternative names

Reed

Commodities and mineralogy

Main commodities Ag; Au; Cu
Ore minerals chalcopyrite; magnetite
Gangue minerals calcite; epidote; garnet; pyroxene; quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale C-2
Latitude 55.57781
Longitude -132.46482
Nearby scientific data Find additional scientific data near this location
Location and accuracy The It Mine is located by name on the USGS 1:63,360-scale topographic map; it is about 0.3 mile south of the center of section 36, T. 72 S., R. 84 E. The geology and workings of the It Mine are shown on Plates 23 and 24 of Warner and others (1961).

Geologic setting

Geologic description

The metamorphic rocks at the It Mine consist of thick, northwest-trending, bands and lenses of garnet-epidote-quartz-calcite-pyroxene skarn, marble, and greenstone (Warner and others, 1961; Myers, 1985). They have been intruded by a northwest-trending, irregular band of diorite up to about 700 feet wide, and by several basalt, andesite, diabase, and gabbro dikes.
The best ore in the main workings, most of which is mined out, was localized along the contact of skarn and lenses of marble; individual ore shoots have been mined to a depth of about 350 feet. Similar but less extensive ore occurs at the north workings. The ore minerals are mainly pyrite and chalcopyrite. Magnetite is sparse in the mine workings although several small magnetite bodies were found nearby. In his detailed study of the mine, Myers (1985) noted that the skarns are dominated by the association garnet-epidote-quartz-calcite with minor magnetite after platy hematite. The ore has relatively high silver values, greater than 200 parts per million (ppm), and gold values of less than 10 ppm.
The mine has two groups of workings. The main workings consist of two glory holes, 3 adits, several open cuts, and a few trenches. The north workings, about a quarter of a mile northwest of the main workings, consist of a glory hole, two adits, and numerous pits and trenches. The detailed geology of the mine and locations of the numerous workings are shown on plate 23 of Warner and others (1961) and in Myers (1985).
Development began in 1907 and the first shipment of copper ore was in 1908. Except for two years, the mine produced steadily until 1918, principally by Granby Consolidated Mining, Smelting, and Power Company. About $1,000,000 in copper was produced. Maas and others (1995) give the total production as 2,030 tons of copper, 28,970 ounces of silver, and 4,372 ounces of gold. The average grade of the ore was 3.99 percent copper, 0.0685 ounce of gold per ton, and 0.478 ounce of silver per ton. Granby reportedly mined out the deposit and was unsuccessful in finding any additional ore bodies in spite of extensive diamond drilling.
The Reed prospect nearby is similar (Wright, 1909) and may be part of this mine or the nearby Alarm (CR055) Mine.
The It Mine is one of many copper-iron deposits on the Kasaan Peninsula having similar geology and origin (Warner and others, 1961; Eberlein and others, 1983; Brew, 1996). The rocks on the peninsula consist mainly of andesite ('greenstone' in much of the older literature) interbedded with about 25 percent sedimentary rocks comprising approximately equal amounts of limestone or marble, calcareous mudstone and sandstone, and graywacke and conglomerate. These units are part of the Luck Creek Breccia of Silurian and Devonian age, but many of the sedimentary units are similar to and probably grade into rocks of the Silurian and Ordovician, Descon Formation. The bedded rocks are intruded by a profusion of Silurian or Ordovician dikes, sills, and irregular masses of porphyritic gabbro, basalt, andesite, diorite, dacite, and granodiorite. Near some of the deposits, these intrusions may make up 20 percent or more of the outcrop and usually are associated with the development of tactite and alteration of the greenstone. The area subsequently was intruded by several large Silurian or Ordovician plutons; they are mainly granodiorite but locally are diorite and gabbro.
The ore deposits are typically small and of irregular shape; often the ore bodies form lenses or mantos. Some of the deposits conform to the layering in the greenstone and sedimentary rocks. The principal ore minerals are chalcopyrite, pyrite, and magnetite; hematite is often present and a little molybdenite occurs in some deposits. Most of the deposits are associated with tactite or skarn with varying amounts of actinolite, calcite, chlorite, garnet, diopside, epidote, and hornblende. There was significant by-product silver and gold in the ore that was mined in the past, and the gold values in some deposits are high enough to have encouraged exploration in recent years. Marble is more common in the deposits in the western part of the peninsula, where the gold values are generally higher as well (Wright and Wright, 1908; Wright, 1915; Warner and others, 1961; Myers, 1985; Bond, 1993; Maas and others, 1995).
Early interpretations of the ore deposits on the Kasaan Peninsula emphasize their contact metamorphic origin and their probable Mesozoic age (for example, Warner and others, 1961). However, recent radiometric dating and mapping indicate that the deposits formed in a Silurian or Ordovician, arc-related environment characterized by deposition of andesite and submarine sedimentary rocks that were intruded by swarms of dikes of varying composition, mineralized, and then intruded by large granodiorite plutons (Hedderly-Smith, 1999 [Inventory]).
The copper deposits of the Kasaan Peninsula were known to the Russians and the first claim was staked in 1867. Most of the production and development occurred from about 1900 to 1918, especially from 1905 to 1907, when copper prices soared and a smelter was built at Hadley on the north side of the Kasaan Peninsula. After World War I, copper supply exceeded demand, prices fell, and there has been no further copper production since 1918 (Wright, 1915; Warner and others, 1961; Roppel, 1991; Maas and others, 1995). However, because of the intense and widespread mineralization on the peninsula, the area has repeatedly been re-examined for copper, iron, and gold, notably during WW II (Warner and others, 1961) and in the last several decades.
Geologic map unit (-132.466497248118, 55.5774411044686)
Mineral deposit model Cu-Fe skarn (Cox and Singer, 1986; model 18d).
Mineral deposit model number 18d
Age of mineralization The deposit formed in a Silurian or Ordovician, submarine arc-related environment characterized by the deposition of volcanic and sedimentary rocks, the intrusion of swarms of dikes of diverse composition, and the emplacement of several large plutons.
Alteration of deposit Development of calc-silicate skarn.

Production and reserves

Workings or exploration The mine has two groups of workings. The main workings consist of two glory holes, 3 adits, several open cuts, and a few trenches. The north workings, about a quarter of a mile northwest of the main workings, consist of a glory hole, two adits, and numerous pits and trenches. The detailed geology of the mine and locations of the numerous workings are shown on plate 23 of Warner and others (1961) and in Myers (1985). Development began in 1907 and the first shipment of copper ore was in 1908. Except for two years, the mine produced steadily until 1918, principally by Granby Consolidated Mining, Smelting, and Power Company.
Indication of production Yes; medium
Reserve estimates Probably none left. Granby Mining, Smelting, and Power Company reportedly mined out the deposit by 1919 and was unsuccessful in finding any additional ore bodies despite extensive diamond drilling.
Production notes About $1,000,000 in copper was produced. Maas and others (1995) give the total production as 2,030 tons of copper, 28,970 ounces of silver, and 4,372 ounces of gold.

Additional comments

The patented claims of the It Mine were purchased by the Sealaska Corporation in 1998.

References

MRDS Number A010131; A010159

References

Bond, R.W., 1993; The mineralogy and geochemistry of the Kasaan Peninsula, iron-copper-silver-gold skarns, Prince of Wales Island, southeastern Alaska: Salt Lake City, University of Utah, M.Sc. thesis, 130 p.
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Myers, G.L., 1985, Geology and geochemistry of the iron-copper-gold skarns of Kasaan Peninsula, Alaska: Fairbanks, University of Alaska, M.Sc. thesis, 165 p.
Roppel, Patricia, 1991, Fortunes from the earth: Manhattan, Kansas, Sunflower University Press, 139 p.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1915: U.S. Bureau of Mines Bulletin 142, 65 p.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1916: U.S. Bureau of Mines Bulletin 153, 89 p.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004