Pyramid Peak, Ruby Mine

Mine, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Pb; Zn
Ore minerals chalcopyrite; gold; pyrite
Gangue minerals limonite; quartz

Geographic location

Quadrangle map, 1:250,000-scale UN
Quadrangle map, 1:63,360-scale D-2
Latitude 53.8583
Longitude -166.54
Nearby scientific data Find additional scientific data near this location
Location and accuracy Location is on northwest slope of Pyramid Peak, near Obernoi Point; 2 km southwest of Unalaska Village at elevation of about 1500 feet (50 m), it corresponds to locality 2 of Cobb (1972, MF-446). Latitude and longitude are accurate to within about 200 m.

Geologic setting

Geologic description

According to Collier (1905) and Simpson (1986), this historic mine was developed on quartz veins localized on vertical joint sets in andesitic volcaniclastic rocks of the Unalaska Formation. An adit approximately 300 feet (60 m) deep followed the veins and joints in the andesitic rocks. The main vein varies in width from 6 feet (2 m) at widest part to 1 foot (0.3 m) at ends of tunnels and crosscuts. This colorless to tan quartz vein contains very fine-grained visible gold (< 1 mm) and trace pyrite and chalcopyrite. The tan color is thought to be due to very fine-grained oxidized pyrite (Simpson(1986). Underground, the quartz breccia/vein zone varies from 40 feet (12 m) wide to as much as 80 (24 m) on the east. Quartz is similiar to that on surface and also contains open spaces having crystals to 1/4' (6 mm) long. Samples collected by Simpson (1986) underground from a small stockpile near a winze contained visible galena, chalcopyrite, and sphalerite. From this, he concluded that sulfide concentration apparently increases with depth. Numerous dikes cut tuffs and flows of the country rock. Above the adit the bedrock is well exposed, below it exposures are non-existent due to thick vegetation (Simpson, 1986).
Geologic map unit (-166.541891633797, 53.8574384713533)
Mineral deposit model Epithermal gold vein
Mineral deposit model number 25
Age of mineralization Late Tertiary or younger
Alteration of deposit Regional propylitic alteration; wall rocks show little or no wall rock alteration.

Production and reserves

Workings or exploration According to Collier (1905) the main tunnel runs east about 20 feet (7 m), then south approximately 150 feet (45 m) crosscutting joints and main ore body, which are developed by short drifts. Tunnel then turns east and follows little-mineralized joint for several hundred feet (> 60 m). A cable tramway had connected mine with 3-stamp mill, both of which were in ruins by 1904. Collier (1905) reports assay of 0.02 oz/ton gold (about 0.7 ppm), and a trace of silver from the face of a drift on the main ore body. Kennecott-Alaska channel samples across vein ranged between 0.1 and 0.9 ppm gold (Simpson, 1986). Undescribed samples collected underground by Kennecott-Alaska (Simpson, 1986) contained up to 1.15 ppm gold, 9.4 ppm silver, 3,000 ppm copper, 8,070 ppm lead, and 4,200 ppm zinc.
Indication of production Yes; small
Production notes Construction of a mill and extensive underground workings suggest some production. However, Simpson (1986) expressed opinion that no ore was probably ever shipped.

Additional comments

The mill was apparently constructed on the basis of very high assays, which were not realized at the time of milling (Collier, 1905). Mill was apparently moved from the Apollo Mine (PM006) on Unga Island (Norton, 1907). Other undescribed occurrences are nearby according to Simpson (1986).

References

MRDS Number A013232

References

Jaggar, T.A., Jr., 1908, Journal of the Technology Expedition to the Aleutian Islands, 1907: Technology Review, v. 10, no. 1, p. 1-37.
Norton, L.M., editor, 1907, Boston Alaskan (published in the interests of Alaska): Boston-Alaskan Society, v. 1, August, 1906-June 1907, 175 p.
Simpson, D.F., 1986, Aleutian Islands project, 1985 final report: Kennecott Alaska Exploration Company, 54 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)
Reporters L.P. Niles; S.W. Bie; F.H. Wilson
Last report date 5/6/1996