Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Hg
Ore minerals pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PM
Quadrangle map, 1:63,360-scale B-2
Latitude 55.28
Longitude -160.599
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Thormac occurrence is approximately 1.5 miles southwest of Ben Green Bight on Unga Island (Wilson and others, 1988, locality 42). The map site is at an elevation of about 1,150 feet, in the NE1/4 of sec. 1, T. 57 S., R. 75 W., of the Seward Meridian. The location is accurate to within 1,000 feet.

Geologic setting

Geologic description

This occurrence is a quartz vein system with a strike length of 1,100 feet. Individual veins within the system exceed 3 feet in width. The host rock is andesite of the late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995). The system contains abundant gossanous vugs. There is no indication of base metal sulfides, and the gossans probably reflect oxidation of pyrite. Grab samples contained 0.005 to 0.135 ppm gold, 0.2 to 19.0 ppm silver, as much as 800 ppm arsenic, and 5.0 ppm or more mercury (Peterson and others, 1982).
Geologic map unit (-160.601032245003, 55.2791727069344)
Mineral deposit model Epithermal gold vein
Age of mineralization Eocene or younger.

Production and reserves

Workings or exploration In 1982 UNC Teton Exploration Drilling Company explored the occurrence and collected several samples.
Indication of production None

Additional comments

This site is located on land either selected or patented by, or interim-conveyed to, the Aleut Corporation.


MRDS Number 10308128


Peterson, R.J., Lemmers, J., Handverger, P., Gallagher, J., Pilcher, R., East, J., Macleod, T., Bartels. E., 1982, Geology and precious metals potential Unga, Popof, and Korovin Islands, Shumagin Group, Aleutian Chain, Alaska: UNC Teton Exploration Drilling Company report, 127 p., 5 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher
Last report date 1/15/2001