A method and system for converting copper cyanide to copper oxide is provided. The method includes contacting a copper cyanide solution with an acidic solution in a precipitation tank under reaction conditions sufficient to produce a copper cyanide slurry, removing the copper cyanide slurry from the precipitation tank, separating solid copper cyanide from the copper cyanide slurry in a first separation device, removing the solid copper cyanide from the first separation device, contacting the solid copper cyanide with a sodium hydroxide solution in a production tank under reaction conditions sufficient to produce a copper oxide slurry, removing the copper oxide slurry from the production tank, separating solid copper oxide from the copper oxide slurry in a second separation device, and removing from the second separation device any residual sodium hydroxide not reacted during the process of contacting the solid copper cyanide with the sodium hydroxide solution in the production tank.

An oxidation step for sulfide and transition ores prior to CN leaching to recover 60 to 90 percent of metals from those ores. Use of tona, soda ash or carbonate source in treating sulfide and transition ores for CN leaching recovery of metals, including gold and silver. The oxidation of sulfide and transition ores in the presence of carbonate. Low moisture content in the heap, to enhance available oxygen, during the oxidation of sulfide and transition ores in the presence of carbonate.