Abstract: The present invention is directed to a precious metal recovery process in which basic ferric sulphates and/or jarosites are controlled by a number of mechanisms, including control of the oxidation reaction conditions in the first autoclave compartment, hot curing of the autoclave discharge slurry, and/or contacting of the autoclave feed slurry with the hot cured discharge liquid.

Abstract: A hydrometallurgical process to leach at least one base metal from one or more base metal sulphide feeds comprising the steps of providing a base metal sulphide feed; processing at least a portion of the feed by roasting to reduce the content of sulphur therein to a predetermined sulphur content level; directing some or all of the processed feed with or without some of the unprocessed feed to an oxidative leach step to carry out an oxidative leach step under conditions sufficient to recover at least a portion of the base metal from the feed, the predetermined sulphur content level being selected so as not to exceed that which is required to provide a source of heat for the oxidative leach step and to provide sufficient sulphate to complex the portion of the base metal being recovered