Millennium Minerals has appointed engineering firm Ausenco to complete a feasibility study on an alternate processing option as part of its sulphide ore expansion study at the Nullagine gold project in Western Australia.
The expansion study, which is aimed at unlocking the full economic potential at Nullagine and identifying pathways to process the large sulphide resource inventory, was largely completed last quarter.
The study was originally based on a preferred plant and configuration comprising an integrated CIL and flotation circuit.
This expansion pathway would involve the integration of a flotation circuit capable of treating sulphide ore with an existing 2 million tonne a year (Mt/y) CIL plant.
According to Millennium, the study confirmed that capital expenditure required to fund the plant modifications would be around $40–46 million.
Working with MineScope Services, Millennium has identified an alternative processing configuration, which could result in a reduction in both capital and operating costs compared with the integrated CIL and flotation circuit, while also delivering several benefits to its expansion plans.
The basis of the new process method is scavenging un-leached sulphide concentrates from the existing CIL tailings and subjecting them to ultra-fine grinding and intense cyanidation to achieve an improvement in the overall leach recovery.
Millennium said financial estimates have indicated the new option has potential to reduce the capital cost to $12–15 million.
Peter Cash, Millennium chief executive, said the expansion study, which underpinned the company’s corporate objective of becoming a 100,000 ounce a year (oz/y) producer by unlocking the large sulphide mineral resource inventory at Nullagine, was in its final stages.
“The identification of this new processing option could transform the economics of the expansion project, dramatically reducing both capital and operating costs and resulting in a major reassessment of our reserve inventory,” Cash said.