PERTH (miningweekly.com) – Gold developer Wiluna Mining has reported a 142% increase in its gold reserves at its Wiluna underground operation, in Western Australia.

The project is now estimated to host an underground ore reserve of 4.33-million tonnes, grading 4.474 g/t gold for 661 000 oz of contained gold, up from the previous estimate of 1.78-million tonnes, grading 4.77 g/t gold for 273 000 oz of contained gold.

Total ore reserve at the project now stood at 37.6-million tonnnes, grading 1.09 g/t gold for 1.32-million ounces, a 53% increase on the previous reserve tonne estimate.

“The 2020 ore reserve increase for Wiluna is the result of the focused efforts of our geological and mining teams over the past 18 months to grow our resources, convert our inferred material to indicated or measured, and to prepare for our transition to gold in concentrate production,” said Wiluna executive chairperson Milan Jerkovic.

“This mineral resource expansion has underpinned the 661 000 oz underground Stage 1 ore reserve we announced today. This ore reserve is sufficient to support a five-year operation at 750 000 t/y Stage 1 processing rates and provides a sound base upon which to further develop the mineral resource and ore reserves for the long life operation we expect Wiluna to be.”

Jerkovic said that despite the openpit ore reserves at Wiluna decreasing, Wiluna Mining continued to investigate ways to bring the mineralisation back to reserve status in the coming years.

“Offsetting this reduction has been the strong improvement in the Wiltails tailings retreatment project economics following additional mineral resource and metallurgical testwork which has expanded the ore reserve from 234 000 oz to 579 999 oz providing the opportunity to generate a steady, long-term gold production stream over a 15-year mine life for the existing carbon-in-leach (CIL) processing plant,” he added.

“The potential for extensions to known mineral resources at Wiluna is considerable and so we will continue to maintain the momentum we have built to methodically infill drill the significant gaps between defined lodes, upgrade inferred mineralisation to indicated or better and to plan for a productive and low cost mining operation.

“Our 2021 drilling programme will continue to target infilling the mineral resource, particularly in the Happy Jack, Bulletin and Essex areas with the intention to add 500 000 oz to the ore reserve base for inclusion in the Stage 2 feasibility study.”

Wiluna Mining earlier this week formalized an agreement with contractor Byrnecut Australia for the performance of underground development and production mining services at Wiluna, over the next five years.

Wiluna has started a three-year staged development plan which is aimed at treating all the ore types at the mine through four processes, including the existing CIL plant, a flotation and concentrator, a gravity circuit and a tailings retreatment plant.