Gold Extraction from Refractory Minerals Using Acid Oxidative ... Leaching cyanidation tests were carried out at pressure = 1 atm and temperature = 25 °C; first leaching of the sulfide concentrate without any pretreating, gold extraction reached % with the following conditions: % NaCN, 20% solids, pH =, agitation = 350 rpm, particle size of μm, and time of 24 h.