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Columbium in the Gold- and Tin-Bearing Placer Deposits Near Tofty, Alaska.
For Reference Only At Bureau Libraries :25 pages
The Tofty Mining District, near Manley Hot Springs in north-central Alaska, has been the scene of placer gold mining since 1906 and has produced more than 100,000 tr oz of gold and several hundred tons of byproduct tin, in the form of placer cassiterite. Although opencut mining methods are currently employed, drift-mining methods were formerly utilized to mine the gold- and tin-bearing gravels. As part of the current Bureau of Mines Alaska-wide assessment of critical and strategic minerals, splits of concentrate samples collected in the 1950's from 11 tailings piles representative of the presently inactive Tofty drift mines were reanalyzed in 1983 for tantalum and columbium (niobium). Most of these concentrates contained between 0.2 and 4.5 pct Nb. Tantalum was detected, but not measured, in only three samples. Relatively higher average niobium values from tailings piles on either side of a small hill suggest a possible intrusive source there at shallow depth. Niobium occurs in the Tofty area in the mineral columbite that could be recovered as a byproduct during placer mining of gold and/or tin. An estimated 100,000 lb of recoverable Nb2o5 are inferred to be present in the Tofty placer deposits.
For Reference Only At Bureau Libraries
Alaska Field Operations Center
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division