Yakobi Island

Mine, Undetermined

Alternative names

Miner Island

Commodities and mineralogy

Main commodities Au
Other commodities Cu
Ore minerals chalcopyrite; native gold
Gangue minerals clay (gouge); quartz

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale A-2
Latitude 58.012
Longitude -136.343
Nearby scientific data Find additional scientific data near this location
Location and accuracy The mine is accurately located (to within 0.1 mile) on the shore line of Yakobi island, northwest of Miner Island. It is on the point west of the junction of Lisianski Strait with Lisianski Inlet (west ). The site is location number 64 of Cobb (1972).

Geologic setting

Geologic description

The Yakobi Island gold-quartz vein is within an intrusion of quartz diorite, of Cretaceous age, which forms a major granitic batholith on Chichagof, Baranof, and Yakobi Islands (Loney and others, 1975). A coarse-grained hornblendite occurs within a few feet of the vein deposit.
The mineralized quartz vein is from 1 to 3 feet wide, dips steeply, and strikes northwest. The quartz occurs along a shear zone, associated with clay gouge, in a dark colored phase of the quartz diorite. Locally, the vein contains small amounts of chalcopyrite and native gold. The vein was developed by a short adit; the quartz pinched out in the adit, but was picked up on strike on the surface above the workings, indicating that quartz masses along the shear zone are lenticular (Overbeck, 1919).
Geologic map unit (-136.344835710167, 58.0116168166337)
Mineral deposit model Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Cretaceous or younger.
Alteration of deposit Clay gouge developed along shear zone.

Production and reserves

Workings or exploration A 35-foot-long adit was driven about 1887 on the shear zone, just above tide level. Four claims were active in 1917.
Indication of production Yes; small
Production notes About 55 ounces of gold were produced before 1917.

Additional comments

The site is in Rossman's hypothetical gold belt (plate 16, 1959). The site is in Tongass National Forest on land of unknown mining status.