JOHANNESBURG (miningweekly.com) - ASX-listed Millennium Minerals has appointed consulting engineering firm Ausenco to complete a feasibility study on an alternative processing option for the Nullagine gold project, in Western Australia, which could be more cost effective than its original expansion plan.

The processing option was identified in the sulphide ore expansion study, which seeks to unlock the full economic potential of the Nullagine resource base and to identify pathways to process the large sulphide mineral resource inventory.

The study was originally based on a preferred plant configuration comprising an integrated carbon-in-leach (CIL) and flotation circuit. The expansion would involve the integration of a flotation circuit capable of treating sulphide ore with the existing two-million-tonne-a-year CIL plant.

The alternative processing configuration would scavenge unleached sulphide concentrates from the existing CIL tailings and subject them to ultra-fine grinding and intense cyanidation to achieve an overall improvement in the leach recovery. This is a similar processing configuration that is used to process sulphide ore at other Western Australian gold mines.

The capital expenditure required to fund the plant modifications for the integrated CIL and flotation circuit would be between A$40-million and A$64-million, including contingency. This could be reduced to between A$12-million and A$15-million with the new processing option, Millennium Minerals reported on Monday.

The company is working with MineScope Services principal engineer Dale Harrison and Ausenco to pursue the processing configuration, which Millennium CEO Peter Cash described as a potential game-changer for the project.

"The sulphide ore expansion study, which underpins our corporate objective of becoming a 100 000 oz/y producer by unlocking the existing large sulphide mineral resource inventory at Nullagine, is now in its final and most important stages," Cash enthused.

The completion of the expansion study dovetails with the company's move underground at Nullagine, with the development of the Bartons underground mine set to begin by the end of this quarter.