Geochemical Evaluation of Historic Mill Tailings, Goldfield, Nevada

Approximately four million tons of tailings were generated by the Goldfield Consolidated
Mill Company (GCMC) from 1908–1919 using ball milling, mercury amalgamation
and cyanide leaching to process precious metal ores. The tailings were discharged
by gravity and deposited as an alluvial fan on the flat area below the mill. The
thickness of this tailings fan ranges from 0–12 metres, and it covers an area of over
500,000 m2. Erosion of the tailings has been occurring for almost 100 years, but the
migration of arsenic, selenium, copper, cadmium and lead away from the tailings was
poorly understood. A Rotosonic drill program was employed to assess the downward
extent of constituent migration from the tailings into the underlying alluvium and, in
places, the sedimentary bedrock of the Miocene Siebert Formation.