Ferric chloride leach of a metal-sulphide bearing material

A two stage leach process for leaching a complex, metal-sulphide bearing material, wherein fresh, complex, metal-sulphide bearing material is fed to a first leach stage, wherein the residue of said material from the first leach stage is fed to a second leach stage, wherein, for each of said leach stages, the material to be leached is contacted with a respective aqueous ferric chloride leach solution whereby metal values are brought into solution as chlorides thereof, said leach solutions each comprising a respective oxidizing component, wherein for the first leach stage said fresh complex material is present in stoichiometric excess relative to the oxidizing component of the first stage leach solution, wherein for the second leach stage the oxidizing component of the second stage leach solution is present in stoichiometric excess relative to said residue, characterized in that for each leach stage, the material to be leached is contacted with a respective leach solution in the presence of an effective amount of a leaching aid comprising one or more compounds of general formula (I) ##STR6## wherein Me is an alkali metal,

• Y is a single carbon to carbon bond or an alkylene chain of not more than 4 carbon atoms and
• the R's, the same or different, each represents an alkyl group of 3 to 8 carbon atoms,
• said effective amount being at least about 100 ppm relative to the material to be leached.