Boise antimony

Region West, Northwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area East-west belt of antimony occurrences the Boise Basin- Horseshoe Bend area.
Identified resources Past production of antimony, gold, lead, and silver.
Production Entire production of ore from Hermada was 5,000 tons, containing about 640 ton Sb, of which 550 tons were recovered (Popoff, 1953).
Status Past mining.
Estimated resources Unknown.
Geologic maps Anderson (1934), scale 1:48,768; Anderson (1947a), scale 1:24,000; Kiilsgaard and others (2001), scale 1:100,000.
Geophysical data See McCafferty and Abrams (1991), scale 1:250,000.
Favorable rocks and structures Boise basin quartz diorite of the Idaho batholith.
Deposits Hermada Antimony mine (MRDS dep_id: 10070739), Summit mine, Twin Sister mine (MRDS dep_id: 10105548), Clear Creek mine.
Evidence from mineral occurrences MRDS.
Geochemical evidence Ore at Mountain Chief mine assayed 0.053 oz Au; arsenopyrite sample assayed 1.36 oz Au, 0.7 oz Ag, 2% Bi, 0.3% Pb and 0.6% Sb; see Malcolm and Smith (1991).
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments Because of variable mineralogy related to different stages of metallization, deposits are differentiated into pyritic lodes, base-metal lodes, gold and base-metal lodes, gold-bismuth lodes, gold-quartz lodes, silver-gold lodes, and silver lodes, each of which has certain other distinguishing features of composition (Anderson, 1947a).
Cover thickness and description Veins exposed at the surface; erosion created local placer deposits.
Authors Virginia S. Gillerman, Reed S. Lewis, Christopher A. Tate, Jane M. Hammarstrom.
New data needs Geophysics, good regional mapping exists; mine-scale work stopped in the 1950s but could be added to.
Geologic mapping and modeling needs 1:24,000 scale geologic mapping in progress (STATEMAP).
Geophysical survey and modeling needs High resolution, Rank 1 aeromagnetic and aeroradiometric coverage.
Digital elevation data needs Lidar mostly complete; some areas in progress, small area incomplete.