Boulder Bay

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au
Ore minerals pyrite
Gangue minerals chlorite; epidote

Geographic location

Quadrangle map, 1:250,000-scale UN
Quadrangle map, 1:63,360-scale A-6
Latitude 53.33
Longitude -167.73
Nearby scientific data Find additional scientific data near this location
Location and accuracy Northeast side of Umnak Pass between Boulder Bay and Paso Point on Unalaska Island. Anomaly no. 46 of Christie (1974).

Geologic setting

Geologic description

A small 1,500 ft (450 m) long north-south trending color anomaly is developed in hornfelsed sedimentary, and pyroclastic volcanic rocks of the Unalaska Formation (see Drewes and others, 1961) cut by north-south trending monzonite and feldspar porphyry dikes. Disseminated and fracture-controlled pyrite occurs in both dike and wall rocks. Minor quartz veining is noted in the description of the occurrence as is weak fracturing.
Geologic map unit (-167.73192039236, 53.3291033379538)
Mineral deposit model Epithermal gold vein
Mineral deposit model number 25
Age of mineralization Miocene or younger.
Alteration of deposit Propylitic alteration as evidenced by the presence of chlorite and epidote.

Production and reserves

Workings or exploration Brief reconnaissance mapping and 4 soil or silt samples. Copper, molybdenum, zinc and silver were low, however a few samples showed gold to 0.20 ppm.
Indication of production None


MRDS Number A106026


Christie, J.S., 1974, Aleut-Quintana-Duval 1974 joint venture, final report: Unpublished Quintana Minerals Corporation report, 24 p., 3 appendices, 2 maps. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters Damon Bickerstaff, F.H. Wilson
Last report date 5/6/1994