Abstract: Precious metals such as gold and silver are recovered from difficult-to-treat ores, especially those containing manganese and/or copper, by lixiviating the ores using copper-ammonium thiosulfate in which the pH of the lixiviating solution is maintained at a minimum level of 9.5 in order to inhibit the action of metallic iron and its ferric salts that are present in the solution and which decomposes the double salt of copper-ammonium thiosulfate. Copper cement is used in a subsequent precipitation process to expose a large amount of area on which the gold and silver can precipitate without also causing precipitation of copper from the lixiviant solution.