Leaching of precious and chalcophile metals

A process for recovery of one or more target metals, selected from precious metals and chalcophile metals as respectively herein defined, from materials containing precious and/or chalcophile metals, the process including:

• leaching the material containing metals with an aqueous leaching solution containing:
• a metal liberator comprising an amino acid;
• and
• a metal retainer comprising one or more of ammonia, ammonium salts, carboxylic acids, carboxylic acid salts, dicarboxylic acids, dicarboxylic acid salts, hydroxy-carboxylic acids, hydroxy-carboxylic acid salts, ethylene diamine tetra-acetic acid (EDTA) and EDTA salts,
• to produce a leachate containing the one or more target metals;
• and
• (ii) extracting the one or more target metals from the leachate, wherein the one or more target metals are selected from gold, silver, palladium, platinum, copper, nickel, cobalt and zinc;
• and
• wherein the metal retainer is present in solution at a concentration of at least 0.001 M.