Golden Sunlight is a conventional open-pit mining operation located near Whitehall, Nevada. The process plant consists of a conventional cyanidation circuit but has been modified to include a Sand Tailing Retreatment (STR) process that recovers sulfide materials for finer grinding and higher-intensity leaching.
AuTec personnel were involved in a complete mill survey in late 2013. This survey allowed AuTec to become familiar with the processing facility as well as with the different types of ore processed at Golden Sunlight. It was presumed that finer grinding of the STR material would yield higher recoveries. This was found to be true for some ore types, but for other ore types a true refractory sulfide character was identified. A further complicating factor is the hosting of a significant portion of the gold in telluride minerals, which give slow leaching kinetics.
In combination with testwork to support the next mining area at Golden Sunlight, Bonnie Zone, it was determined that flotation of a high-grade gold-bearing pyrite concentrate for shipment to Goldstrike for processing at the roaster would yield attractive opportunities for both Goldstrike and Golden Sunlight. AuTec is involved in developing this concept further.
Recently, the mine experienced a period of somewhat low gold recovery from relatively high grade gold ore. AuTec personnel were able to attribute the gold losses primarily to the presence of calaverite, a slow-leaching gold telluride. When operators know of the presence of gold-bearing tellurides in the ore, certain operating parameters can be modified to maintain high gold recoveries.