Process for treating ore having recoverable metal values including arsenic containing components

A process for treating ores in the form of ore particles, having recoverable precious metal values and metal values and including arsenic-, carbon- and sulfur-containing components which comprises:

• roasting said ore particles in the presence of at least one substance selected from the group consisting of:
• i. a free oxide, carbonate, sulfate, hydroxide and chloride of calcium, magnesium, iron and barium;
• ii. a pyrite;
• and
• iii. iron;
• in an oxygen augmented atmosphere having a total initial oxygen content of less than about 65% by volume while maintaining a reaction temperature from about 475° C. to about 900° C. during said roasting, without formation of a molten phase on the surface of said ore particles and further wherein said substance is present in an amount at least 1 to 4 times the stoichiometric amount necessary, at least 3.5 times when said substance comprises iron, on mol basis, to react with arsenic in said ore to form stable arsenates;
• roasting said ore in presence of water vapor up to 10% by weight of said ore such that the water vapor content in an exhaust gas from said roasting is 0.5 to 10%;
• and
• recovering a thus-roasted ore as calcine whereby said calcine is amenable to recovery of precious metal values in said calcine.