Stewart Mine, Sitka Borough, Alaska, USA

MAS number: 0021160007.
Location: The Stewart Mine is shown by symbol on the topographic map. It is about 1.9 miles east-southeast of Arguello Island at the head of Silver Bay and about 0.7 mile northwest of the center of section 33, T. 56 S., R. 65 E. The location is accurate and the surface and underground working have been mapped by Bittenbender and others (1999, figs. 18-21).
Geology: This deposit is one of many of similar deposits (PA002 to PA018) scattered over an area of about 6 square miles at the head of Silver Bay (Bittenbender and others, 1999). The deposits are gold-quartz veins with sparse sulfides, usually only pyrite and arsenopyrite. Samples that have been analyzed with modern methods usually show anomalous arsenic even if arsenopyrite is not identified in the rocks, and several parts per million mercury. The veins are often parallel to the bedding of the host rock which is graywacke and argillite of the Sitka Graywacke of Cretaceous age (Loney and others, 1975). Many of the so-called veins in the early literature are actually fault zones with lenses of quartz or concentrations of quartz stringers along the fault zone. Prospecting began in the area in 1871. The Stewart Mine (PA012) was located in 1872 and it was the first lode-gold mine in Alaska. The Silver Bay area has been prospected intermittently to the present but the veins are relatively small and most are low grade. The area has produced relatively little gold, many of the properties have not been active since before 1900, and there has been no production since the early 1940's. The quartz vein that was to become the Stewart Mine was found in 1872 and production began in 1877 from 3 adits (Bittenbender and others, 1999). In 1879 a 10-stamp mill was in operation. The mine closed in 1880 and was mired in litigation until 1892 when it again was active under new ownership. There are no production records and apparently no major work has taken place after 1893. The mine is on a patented claim that is owned by the Sheldon Jackson College in Sitka. Becker described the property in 1898 but the mill was already in ruins. Bittenbender and others (1999, figs. 18-21) mapped and sampled the three adits, the lowest and longest of which is about 190 feet long. The adits were driven along the vein which is exposed in the underground workings for about 200 feet horizontally and 120 feet vertically. The vein is mainly quartz with inclusions of graywacke host rock; the maximum width of the vein is 16 feet and it averages about 5 to 6 feet. The only visible sulfide in the vein is pyrite but arsenopyrite is likely based on the analyses of samples, which generally contained low gold values. The best gold values were 3,130 parts per billion (ppb) over an area of 3 feet by 5 feet and 1,780 ppb across 5 feet of the vein. A sample of the concentrates from the mill contained 57.9 parts per million (ppm) gold, 2,000 ppm lead, more than 1 percent arsenic, and more than 0.1 percent mercury. Wright and Wright (1905) reported that the ore averaged abut $7.50 per ton in gold (about 0.36 ounce of gold per ton).
Workings: The quartz vein that was to become the Stewart Mine was found in 1872 and production began in 1877 from 3 adits (Bittenbender and others, 1999). In 1879 a 10-stamp mill was in operation. The mine closed in 1880 and was mired in litigation until 1892 when it again was active under new ownership. There are no production records and apparently no major work has taken place after 1893.
Age: Cretaceous or younger based on the age of the host rock.
Production: There was probably some production from 1877 to 1880, but no records are available.
Reserves: None.

Commodities (Major) - Au; (Minor) - As, Hg
Development Status: Yes; small
Deposit Model: Low-sulfide, gold-quartz vein (Cox and Singer, 1986; model 36a).

Mineral List

2 entries listed. 2 valid minerals.

References