New Guinea Gold Corporation has successfully implemented heap leaching to augment the vat leaching process at the Sinivit project and is realizing lower unit costs as a result.
Coupled with increases in crushing capacity, the company believes the financial fundamentals of Sinivit have been placed on a firmer foundation.
The percentage of gold in dore increased from 9.5% in July to 14% in August and September thanks to recently instituted operational enhancements. The pattern of processing improvements has continued in more recent results: gold content in October was 24.8% and increased again to 34.2% in November.
The October content was the best result in the past 10 months while the November result was the highest for the prior 16 months.
These results reflect the ongoing improvements, particularly in vat and processing management and the crushing circuit. Overall operations have also benefited from relatively dry weather conditions.
The metallurgical characteristics of the Sinivit ore still to be mined, specifically the increasing copper content, present a challenge to achieving further operational and processing improvements.
The company believes that longer term the project will be better served if processing can transition to using pulverised ore; e.g. milling and leaching of ore in a standard carbon-in-leach/carbon-in-pulp (CIL/CIP) plant. This would yield not only better gold recoveries from in situ mineralization but it would also allow re-processing of the crushed ore presently in vats and on heaps to extract the residual gold, representing about 20,000 ounces.
To confirm the economic viability of such a change will first require further detailed metallurgical testing of leached material in vats, on heaps and the in-ground ore plus pit and plant design to enable an accurate evaluation of the additional capital requirements.
Metallurgical testing has started on both the partially leached material in vats and heaps and on the in situ mineralization. Initial testing indicates that 90% to 98% of the gold could be recoverable when the material is milled to 150 microns (80% passing) and cyanide leached in agitated tanks. Comprehensive metallurgical testing with development of a flow sheet will be completed during second quarter of 2011.
The metallurgical program will also investigate the viability of extracting tellurium from previously processed material as well as in situ mineralization.