Commercial heap biooxidation of refractory gold ores - Revisiting Newmont's successful deployment at Carlin

•Newmont operated a refractory whole-ore biooxidation facility to recover Au.•Bench and pilot-scale testing led to the commercial whole-ore biooxidation process.•Poor economic conditions led to compromises that reduced performance and Au recovery.•Over 10 Mt of ore were processed and produced an estimated 17 t of Au.

Newmont Mining Corporation pioneered the investigation, development, and commercial-scale implementation of refractory gold whole-ore heap biooxidation, during a period spanning 1988-2009 at Carlin, Nevada. Basic and applied research and development from 1988 to 1999 included laboratory test work and increasingly larger pilot test heaps culminating in the full-scale implementation of a process that was estimated to contribute 120,000-180,000 oz/year to Carlin's production between 2000 and 2005. Key parameters that influenced performance of the on-off heap biooxidation process, and factors that led to the discontinuation of the operation are described.