Process mineralogy of select refractory Carlin-type gold ores

CIM Bulletin, Vol. 78, No. 881, 1985

D.M. HAUSEN, Newmont Exploration Limited Danbury, Connecticut

Refractoriness in Carlin-type gold ores results mostly from fine locking of gold in pyrite, locking in various gangue phases, notably quartz, and a "preg robbing" condition attributed to organic carbon. All three conditions may occur in any given deposit, including Newmont's Carlin and Gold Quarry deposits in Nevada, where types of refractoriness occur locally in minor amounts. Measurements of specific gravity, water absorption and screen size distributions of gold in alteration rock types from Gold Quarry show transitional changes from siliceous cherts through decreasingly silicified and increasingly argillized siltstones. Low permeability of siliceous ores contributes to "size dependent" refractoriness in cyanidation test work. Colligative physical and chemical measurements demonstrate that silicified cherty ores are difficult to grind, poorly permeable, and less amenable to cyanidation. Refractoriness in pad or column leaching of coarsely crushed siliceous siltstones and cherts is shown to correlate with interrelated measurable mineralogic and physical parameters.

Keywords: Mineralogy, Process mineralogy, Refractory ores, Gold mineralization, Gold, Water absorption, Specific gravity, Screen-size distribution, Metallurgy.