Abstract: The recovery of metal values such as nickel from a metal bearing source such as lateritic ores in which the metal bearing source is subjected to a reductive roast at an elevated temperature in the range of from about 700.degree. to about 1300.degree. F. in contact with at least one additive and thereafter extracting the metal bearing source in an ammoniacal solution whereby the desired metal such as nickel is leached out and recovered, the yield of the desired metal may be increased by subjecting the source to an annealing process during the reductive roast thereof.

Abstract: The present process involves an improvement in the hydrometallurgical recovery of metal values from metal bearing sources such as ores and the like. When subjecting a metal bearing source to a reductive roast in a reducing atmosphere followed by cooling the reduced metal bearing source, extracting the cooled source and recovering the resultant nickel value, it is possible to utilize a smaller amount of an additive which assists in the recovery of metal values by scrubbing the off-gases from the reductive roast utilizing a fresh metal bearing source feed as the scrubbing material.