Mount Andrew

Mine, Active

Commodities and mineralogy

Main commodities Cu; Fe
Other commodities Ag; Au
Ore minerals chalcopyrite; magnetite; pyrite
Gangue minerals calcite; epidote; garnet; hornblende

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale C-1
Latitude 55.5167
Longitude -132.3021
Nearby scientific data Find additional scientific data near this location
Location and accuracy The location of the Mount Andrew Mine is shown on the USGS 1:63,360-scale topographic map. It is about 0.5 mile north-northwest of the center of section 26, T. 73 S., R. 86 E. The extensive surface and underground workings of the Mount Andrew Mine and the geology of the mine area are shown on plates 7 to 11 of Warner and others (1961).

Geologic setting

Geologic description

The Mount Andrew is one of the principal mines on the Kasaan Peninsula (Wright and Wright, 1908; Wright, 1915; Wright and Tolonen, 1947; Warner and others, 1961; Maas and others, 1995; Hedderly-Smith, 1999 [Inventory]). The host rocks are mainly greenstone, largely altered to tactite composed of garnet, epidote, and hornblende, and scattered small marble lenses. The dominant structure in the deposit is a syncline that outcrops over an area at least 600 feet long and 550 feet wide, and exposes about 550 feet of layered rocks. The syncline trends about N10W. Nearly half the rock in the syncline is massive magnetite in conformable layers or mantos a few feet to 50 feet thick, interlayered with the greenstone. The greenstone and magnetite layers are cut by numerous north-trending, steeply dipping dikes of alkalic granodiorite, gabbro, andesite, and diorite porphyry. Pyrite and chalcopyrite are disseminated widely in the tactite and magnetite; there were probably local concentrations of chalcopyrite-rich ore, but most such high-grade pockets were probably mined prior to 1919.
The Mount Andrew Mine comprises three adits, 4 glory holes, several winzes, and a sublevel, to a depth of about 250 feet. The geology and workings are shown in detail on plates 7 to 11 of Warner and others (1991). The deposit was discovered in 1898 and the first ore was shipped in 1906 to the Tacoma smelter (Wright and Wright, 1915; Warner and others, 1961; Roppel, 1991). There was intermittent production until 1918, but none since. In 1944, the U.S. Bureau of Mines trenched the deposit and drilled 14 holes. The U.S. Geological Survey mapped the deposit in detail from 1942 to 1944. Utah Construction and Mining did geologic mapping and geophysical surveys in 1957 and drilled the deposit from 1960 to 1962 and in 1968.
In 2006, Full Metal Minerals began work at Mount Andrew and they drilled 5 shallow holes that totaled 481 meters to test the periphery of the old surface and underground workings (Full Metal Minerals, 2008, Mount Andrew Property). The holes cut several zones of mineralization including: 1) 13.2 meters that contained 1.41 percent copper, 0.25 gram of gold per ton, and 5.33 grams of silver per ton, 2) 18.0 meters that contained 1.05 percent copper, 0.13 gram of gold per ton, and 4.06 grams of silver per ton, 3) 13.8 meters that contained 1.01 percent copper, 0.11 gram of gold per ton, and 4.40 grams of silver per ton, 4) 7.7 meters that contained 1.53 percent copper, 0.08 gram of gold per ton, and 5.15 grams of silver per ton, and 5) 38.7 meters that contained 0.42 percent copper, 0.09 gram of gold per ton, and 1.40 gram of silver per ton. The work suggests that the mineralization is of the iron oxide-copper-gold deposit in andesitic volcanic rocks and intermediate intrusive rocks that are cut by post-mineralization dikes. In 2007, Full Metal drilled 1,500 meters in another 13 holes and cut several intervals with strong chalcopyrite-magnetite mineralization (Full Metal Minerals, 2008, Mount Andrew Property; 2008, Mount Andrew drilling; 2008, Mount Andrew locations). Some notable intercepts were: 4.89 meters with 4.45 percent copper, 15.25 grams of silver per ton, and 0.89 grams of gold per tonne and 2.95 meters with 3.75 percent copper and 12.44 grams of silver per tonne (with gold values yet to be received).
There have been several estimates of the remaining resources in the Mount Andrew, Stevenstown (CR072), and Mamie (CR073) mines. Warner and others (1961) and Wright and Tolonen (1947) estimate a collective resource of 2,684,000 long tons of ore, of which about 80 percent is in the Mount Andrew deposit. The weighted average grade of this resource is 47.8 percent iron, 0.32 percent copper, and 0.011 ounce of gold and 0.55 ounce of silver per ton (Wright and Tolonen, 1947). Twenhofel (1953) estimated that about 3,500,000 tons of ore remain in the deposits. Carr and Dutton (1959) estimated that the deposits still contain about 2.3 million tons of indicated magnetite ore with 50 percent iron, and 0.91 million tons of inferrred ore. The total production from the Mount Andrew, Stevenstown, and Mamie mines from 1905 to 1918 was about 270,000 tons of ore with an average grade of 2.37 percent copper, and 0.026 ounce of gold and 0.212 ounce of silver per ton (Warner and others, 1961). Little copper-rich ore such as was mined prior to 1919 probably remains.
Warner and others (1961) and Maas and others (1995) describe several geologically similar, small deposits east of the Mount Andrew Mine. They were originally under the same management as the Mount Andrew Mine and some produced small amounts of ore. These include the Peacock, Rico, North Star, Glory, and Good Luck claims, and the Good Luck-Mayflower group.
The Mount Andrew 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 since 1990.
Geologic map unit (-132.303782247975, 55.5163384238333)
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 Pervasive development of tactite.

Production and reserves

Workings or exploration The Mount Andrew Mine comprises three adits, 4 glory holes, several winzes, and a sublevel, to a depth of about 250 feet. The geology and workings are shown in detail on plates 7 to 11 of Warner and others (1991). The deposit was discovered in 1898 and the first ore was shipped in 1906 to the Tacoma smelter (Wright and Wright, 1915; Warner and others, 1961; Roppel, 1991). There was intermittent production until 1918, but none since. In 1944, the U.S. Bureau of Mines trenched the deposit and drilled 14 holes. The U.S. Geological Survey mapped the deposit in detail from 1942 to 1944. Utah Construction and Mining did geologic mapping and geophysical surveys in 1957 and drilled the deposit from 1960 to 1962 and in 1968. In 2006, Full Metal Minerals began work at Mount Andrew ; they drilled 5 shallow holes that totaled 481 meters to test the periphery of the old surface and underground workings (Full Metal Minerals, 2008, Mount Andrew Property). In 2007, Full Metal drilled 1,500 meters in another 13 holes and cut several intervals with strong chalcopyrite-magnetite mineralization (Full Metal Minerals, 2008, Mount Andrew Property; 2008, Mount Andrew drilling; 2008, Mount Andrew locations).
Indication of production Yes; medium
Reserve estimates There have been several estimates of the remaining resources of the Mount Andrew, Stevenstown (CR72), and Mamie (CR73) mines. Warner and others (1961) and Wright and Tolonen (1947) estimate a collective resource of 2,684,000 long tons of ore, of which about 80 percent is in the Mount Andrew deposit. The weighted average grade of this resource is 47.8 percent iron, 0.32 percent copper, and 0.011 ounce of gold and 0.55 ounce of silver per ton (Wright and Tolonen, 1947). Twenhofel (1953) estimated that about 3,500,000 tons of ore remain in the deposits. Carr and Dutton (1959) estimated that the deposits still contain about 2.3 million tons of indicated magnetite ore with 50 percent iron, and 0.91 million tons of inferrred ore. Little copper-rich ore such as was mined prior to 1919 probably remains.
Production notes No figures are available solely for the production of the Mount Andrew Mine. However, the cumulative production from it and the nearby Stevenstown (CR072) and Mamie (CR073) mines from 1905 to 1918 was about 270,000 tons of ore with an average grade of 2.37 percent copper, and 0.026 ounce of gold and 0.212 ounce of silver per ton (Warner and others, 1961).

Additional comments

The Mount Andrews Mine is covered by patented claims. The Sealaska Corporation holds the subsurface rights to the land around it.

References

MRDS Number A010096; A010103

References

Anzman, J.R., 1995, Airborne geophysical survey, Kasaan Peninsula, Alaska, 12 p. (Unpublished report held by Sealaska Corporation, Juneau, Alaska).
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.
Full Metal Minerals, 2008 (Mount Andrew drilling), 2006-2007 drill hole locations: http://www.fullmetalminerals.com/i/misc/07J03_2007Field_DHLocations_West_300dpi.jpg (as of March 4, 2008).
Full Metal Minerals, 2008 (Mount Andrew locations): http://www.fullmetalminerals.com/i/misc/07J03_2007Field_DHLocations_East_300dpi.jpg (as of March 4, 2008).
Full Metal Minerals, 2008 (Mount Andrew Property): http://www.fullmetalminerals.com/s/MtAndrew.asp (as of March 4, 2008).
Hedderly-Smith, D.A., 1997, Report on the 1995 and 1996 work on the Kasaan Peninsula-Sealaska minerals project: Sealaska Corporation, 87 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1998, Report of the 1995-1997 work on the Kasaan Peninsula-Sealaska minerals project: Sealaska Corporation, 130 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
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).
Hedderly-Smith, D.A., 1999, Results of 1998 work on the Kasaan Peninsula-Sealaska minerals reconnaissance project: Sealaska Corporation, 40 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Mount Andrew Mining Company, 1960, Drill logs and drill maps from the Mt. Andrew property, Prince of Wales Island, Alaska. (Unpublished data held by the Bureau of Land Management, Mineral Information Center, 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.
Nordine, G., 1972, 1971-1972 diamond drilling at Mt. Andrew, Prince of Wales Island, Alaska: Kaiser Resources, 57 p. (Unpublished report held by the Bureau of Land Management, Mineral Information Center, Juneau, Alaska.)
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.
Thorne, R.L., Holt, A.W., Tolonen, A.W., Wright, W.S., and Fosse, E.L., 1945, Mount Andrew iron deposit, Kasaan Peninsula, Prince of Wales Island, southeastern Alaska: Draft War Minerals Report, 42 p.
Reporters D.J. Grybeck (Port Ludlow, WA)
Last report date 3/4/2008