Flagstaff Mine (Last Chance Mine; Treasure Mine), Karta River Wilderness, Prince of Wales Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
Flagstaff Mine (Last Chance Mine; Treasure Mine)	Mine
Karta River Wilderness	Wilderness Area
Prince of Wales Island	Island
Ketchikan Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

This mine is in the Karta River Wilderness Area, and any area which is not already a valid claim or is patented is closed to exploration and mining.

Location: The Flagstaff Mine is a well-known property on the east side of Granite Mountain. The workings are extensive and the location used here is the main adit of the mine at an elevation of about 1,400 feet. This adit is shown on the USGS 1:63,360-scale topographic map; it is about 0.5 mile southwest of the center of section 16, T73S, R84E.

Geology: The rocks in the vicinity of the Flagstaff Mine are part of a large granodiorite-quartz diorite stock (Sainsbury, 1961; Eberlein and others, 1983; Brew, 1996). Early workers considered the stock to be Mesozoic or Cretaceous, but recent radiometric dating indicates that it is Devonian (S.M. Karl, oral communication, 2003). The granitic rocks are cut by diabase dikes of unknown age. Roppel (2005) provides much detail on the history of the mine. The property was originally staked in 1902 as the Treasure group; by 1905, it had been developed by a lower 400-foot adit and an upper 50-foot adit and a road had been built from Karta Bay to Salmon Lake and from Salmon Lake to the mine. The 400-foot tunnel became the main adit of the mine (Wright and Wright, 1908; Twenhofel and others, 1949; Stewart, 1938, 1944; Maas and others, 1991, 1995). By 1908, the original locator of the property relinquished it and in 1912, the claims were restaked by T.N. Steven as the Last Chance Group; he would hold the property for the next 22 years. By 1935, Stevens or leaseholders had extended the upper tunnel to 432 feet and the lower tunnel to 987 feet. In 1937, the Flagstaff Mining Company was formed to develop the property and they rebuilt the road, built several buildings at the property and a 2,000-foot tramway to the main adit, and built a 25-ton mill at the bottom of the tramway. The mill was run intermittently in 1936 and 1938 but the recovery of gold was poor. Mining and milling continued intermittently until the fall of 1941 when the property reverted to its original owners and the mine closed. Poor gold and silver recovery in the mill is cited as a major cause of the closure. There is no record of production since 1941 but several companies have examined the property; among the more intensive efforts, El Paso Mining and Milling Company examined the property in the mid-70's and Killick Gold Company, Ltd. optioned the property and did geological mapping and geochemical surveys from 1980 to 1988. The property has two vein systems. The main workings of the mine are on a quartz vein-the lower or Flagstaff vein-that can be traced for nearly a mile through a vertical extent of at least 1,300 feet. The vein strikes about N55W and dips 60-86NE. The footwall of the vein is a diabase dike more than 8 feet thick that near the vein is almost completely altered to calcite, chlorite, and brown clay. Twenhofel and others (1949) describe the hanging wall as diorite and gabbro. Detailed maps of the main vein are on Plate 1 of Twenhofel and others (1949) and on several appendices in Stewart (1944). The vein varies from less than an inch to more than 36 inches thick; it averages about 18 inches thick but the thickness often varies abruptly. The vein is white, vuggy quartz with free gold and locally abundant sulfide minerals that in many places are banded parallel to the vein. The sulfide minerals include galena, chalcopyrite, pyrite, bornite, and sphalerite. Native copper, covellite, and chalcocite occur and may be secondary. The sulfides average 1-2 percent of the vein but may form up to 5 percent locally. The main vein has been sampled several times (see Stewart, 1944, in particular). There are high gold and silver values, but the data are not systematic enough to provide their average values in the vein. The mill operators told Stewart (1938) that the ore was running about $25 to $35 in gold and silver (with gold at $35 per ounce). Maas and others (1991) sampled the main vein. One sample across 2.5 feet of the vein contained 0.35 ounce of gold per ton, 10.77 ounces of silver per ton, and 7.04 percent lead. The weighted average of 4 other samples was 0.15 ounce of gold and 1.75 ounces of silver per ton across an average width of 1.9 feet. The upper vein is exposed west of the main workings of the mine between about 2, 600 to 2,800 feet elevation near the top of Granite Mountain. This vein strikes about N25E and dips about 20NW, but it is cut by several cross faults and/or deflects markedly and varies in strike and dip. It varies in width from about 1 to 3 feet. The upper vein is similar to the lower vein, but it is mainly in quartz diorite. The intersection of the two veins has not been found. The upper vein has fewer sulfides but more free gold than the lower vein. Maas and others (1995) give the total production of the Flagstaff Mine as 257 ounces of gold, 1,980 ounces of silver, 2,864 pounds of copper, and 5,926 pounds of lead from 873 tons of ore; however, they cite another report that gives the total production from 1938 to 1940 as 1,305 tons of ore.

Workings: Roppel (2005) provides much detail on the history of the mine. The property was originally staked in 1902 as the Treasure group; by 1905, it had been developed by a lower 400-foot adit and an upper 50-foot adit and a road had been built from Karta Bay to Salmon Lake and from Salmon Lake to the mine. The 400-foot tunnel became the main adit of the mine (Wright and Wright, 1908; Twenhofel and others, 1949; Stewart, 1938, 1944; Maas and others, 1991, 1995). By 1908, the original locator of the property relinquished it and in 1912, the claims were restaked by T.N. Steven as the Last Chance Group; he would hold the property for the next 22 years. By 1935, Stevens or leaseholders had extended the upper tunnel to 432 feet and the lower tunnel to 987 feet. In 1937, the Flagstaff Mining Company was formed to develop the property and they rebuilt the road, built several buildings at the property and a 2,000-foot tramway to the main adit, and built a 25-ton mill at the bottom of the tramway. The mill was run intermittently in 1938 and 1938 but the recovery of gold was poor. Mining and milling continued intermittently until the fall of 1941 when the property reverted to its original owners and the mine closed. Poor gold and silver recovery in the mill is cited as a major cause of the closure. There is no record of production since 1941 but several companies have examined the property; among the more intensive efforts, El Paso Mining and Milling Company examined the property in the mid-70's and Killick Gold Company, Ltd. optioned the property and did geological mapping and geochemical surveys from 1980 to 1988.

Age: Unknown, other than that the veins are in Devonian granitic rocks.

Alteration: Diabase dikes are almost totally altered to chlorite, calcite, and brown clay near the veins.

Production: Maas and others (1995) give the total production of the Flagstaff Mine as 257 ounces of gold, 1,980 ounces of silver, 2,864 pounds of copper, and 5,926 pounds of lead from 873 tons of ore; however, they cite another report that gives the total production from 1938 to 1940 as 1,305 tons of ore.

Reserves: Probably none.

Commodities (Major) - Ag, Au, Pb; (Minor) - Cu, Zn

Development Status: Yes; small

Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).

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Link to USGS - Alaska:	CR043

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References