Abstract: Gold-bearing ore of sedimentary origin containing organic carbonaceous material and gold-bearing sulfides is treated to increase the recovery of the gold content thereof by standard cyanidation practice. An aqueous slurry of the finely ground ore is first subjected to a preliminary oxidation treatment wherein air or oxygen is bubbled through the slurry while maintaining the slurry at a temperature of from 167.degree. to 212.degree. F. for a period of from 8 to 24 hours. The oxygenated slurry is then cooled to a temperature of from 70.degree. to 125.degree. F. and acid is added to bring the pH of the slurry down to 6.0 of lower. Chlorine gas or an alkali metal or alkaline earth metal hypochlorite is then added to the slurry unitl the slurry will no longer absorb or react with these reagents. The thus treated slurry is maintained at a temperature of from 70.degree. to 125.degree. F. for a period of from 6 to 12 hours.

Abstract: When certain sedimentary gold ores containing indigenous organic carbonaceous materials are slurried with an aqueous solution containing an alkali metal cyanide, the aurocyanide complex which is formed is adsorbed by an adsorptive carbon component of the ore. Dissolution of the gold proceeds until chemical equilibrium is attained between the aurocyanide complex in solution and the aurocyanide complex adsorbed by the ore. In the process of the invention, the gold is dissolved from the ore by using (1) much higher strengths of cyanide solution, and (2) much higher temperatures than are normally used in the standard cyanidation process, allowing higher extractions of gold to take place. Because the concentration of aurocyanide in solution is limited by chemical equilibrium, the dissolution of gold must be done in stages.

Abstract: The recoverability by cyanidation of the gold content of sedimentary gold-bearing ores containing organic carbonaceous material and gold-bearing pyrite, or other gold-bearing sulfides, is greatly increased by heating an aqueous slurry of the ore to about 167.degree. to 212.degree. F. and then introducing air or oxygen into the heated slurry to oxidize and eliminate a substantial portion of the carbonaceous material and oxidizable sulfides in the slurried ore, followed by cooling the slurry to about 70.degree. to 85.degree. F. and then introducing chlorine gas into the slurry to substantially complete the oxidation and chlorination of the carbonaceous content of the slurried ore. The ore is then subjected to conventional cyanidation to recover the gold content thereof.