The present invention provides an atmospheric acid leaching process for leaching nickel and cobalt from highly-serpentinized saprolitic fractions of nickel laterite deposits that are generally too low in nickel to support economical extraction of their nickel contents by pyrometallurgical processing except under special circumstances, and generally too high in magnesium to be suitable for processing by modern high pressure acid leaching processes employed for treating predominantly limonitic nickel laterites. The process involves leaching the highly-serpentinized saprolitic portion of the nickel laterite ore profile in strong sulphuric acid solutions at atmospheric pressure and temperatures between 80° C. and 100° C., essentially autogenously, to extract at least 90% of its contained nickel content and a large proportion of its cobalt content after leaching reaction times of about one hour or less. The reaction times of one hour or less are comparable with the reaction times employed in the high temperature/high pressure leaching of limonitic laterites. The amount of sulphuric acid used in the leaching process is between about 80% and 100% by weight of the finely ground highly-serpentinized saprolite ore on a dry weight basis. The metal values are recovered as intermediate products.
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