Comparative Cyanide and Thiourea Extraction of Gold Based on Characterization Studies (TECHNICAL NOTE)

Abstract

This study involved preliminary laboratory test work to identify the relative leaching response to cyanidation and thiourea leaching of an oxidized low grade gold ore based on characterization studies. Huge reserves of gold deposits have been reported from different parts of Iran, especially at Neishaboor area with gold grade of approx 4 ppm. For the mineralogical composition, the nature of the minerals, type of gold, chemical characters and the suitable mesh of grind which play vital role in finding out suitable flow sheet design, the representative samples were subjected to detailed characterization studies and found that, the ore is oxidized and gold is present partly in the from of solution in quartz veins as well as in the form of free particles in iron hydroxide specially hematite which is the product of pyrite oxidation. Quartz, hematite, calcite and feldspar are the main minerals present in the order of abundances. Sieve analysis and distribution of gold particles in different sieve fractions shows most of the gold are distributed bellow 2000 microns. Therefore based on characterization studies, the potential of an alternative lixiviant like thiourea leach have been determined and found that under optimized conditions cyanide leaching of the ore performs(extraction of 95% after 240 hours) better than thiourea leaching (extraction of 10% after 240 hours and 67% after 662 hours).