Evolution Of Solution Application For Heap Leach Mining

Heap leach mining has long been an economical method for mining oxide copper ore, and with the U.S. Bureau of Mines' discovery of a way to economically strip gold and silver from carbon, it has become the standard in the gold and silver indus­try as well. Sulfide leach in copper recovery has always been a byproduct of oxide leach mining, although the methods and recovery rates have increased with technology. SX-EW has kindled a new interest in large deposits and dormant dumps of low grade sul­fide ore. Gold ore bio-oxidation was developed in the 1980's, but not tried on a large scale until US Gold built the Tonkin Springs Mine. This mine was dedicated to the large scale production of low grade sulfide ore that could be recovered through the newly discovered bio-oxidation method. On a small scale the method worked, but as time went on, problems with the process were costly and recovery was poor. US Gold did not have the finan­cial backing to perfect the process, and the mine was closed in 1990. Since that time, Newmont Gold Company has taken the lead and has dedicated a lot of resources to the perfection and implementation of this method. Some small mines have discov­ered that if they can use this technology they may be able to dou­ble and triple current ore reserves, because they will be able to mine deposits previously considered not to be economical.