Effect of roasting and ammonia leaching on the mineralogy of multimetal sulphides

Abstract

This paper describes the significance of mineralogy applied to metal extraction from complex sulphide ores of Ambaji (Ambamata) origin, Gujarat, India. The textural associations of various sulphide minerals in the ore as such, are described first and followed by a description of the original intergrowth of minerals still retained in the bulk concentrates. An effort has been made to characterise the mineralogical changes that occur during roasting or during ammonia leaching of Cu-Zn-Pb bulls concentrates. The data, thus generated, are found useful for identification of various mineral phases of partial roast/leach residues thereby making it possible to relate the extraction process to mineral/ore structures so as to achieve specific results. For example, some originally intergrown particles may still be present in the bulk concentates even after heating to approximately 800 degrees C. The liberated independent grains undergo sequential oxidation steps during roasting or during oxidative ammonia leaching. Reaction sequence thus deduced from the oxidation behaviour of multimetal sulphides is compared with thermodynamic stability data on sulphide minerals from the literature.