The company said the “breakthrough” put it on a pathway to achieve its aim of a 100,000 ounce per annum production profile, and opened up the potential for third party toll treatment deals.

Millennium had originally planned to build a stand-alone flotation circuit to process 500,000 tonnes per annum of sulphide ore, but now believes an integrated CIL and flotation plant “will deliver superior results”.

Testwork has achieved recoveries of up to 90% via CIL treatment of fresh ore from its Bartons and Shearers deposits, which can be processed in the existing plant, and recoveries averaging 89% from fresh ore sources including Golden Gate using flotation to produce a precious metal concentrate.

“The ability to process any ore type at Nullagine in the future as and when our mining schedule determines will give us unparalleled ability to exploit the vast resource inventory across the project,” CEO Peter Cash said.

The plant will process 1.5Mtpa when treating 100% fresh ore rather than the current CIL capacity of 2Mtpa for treating about 80% oxide and 20% fresh ore.

The company produced 18,983oz at an all-in sustaining cost of A$1386/oz in the June quarter, which was in line with revised guidance after interruptions to mining and haulage from heavy rain.

Revised full year guidance is for production of 75,000-80,000oz at an AISC of $1360-$1390/oz due the weather interruptions and the forecast cost of the single large cut-back at the Bartons deposit.

Millennium ended the June quarter with $27.7 million in cash and bullion – same as at the end of March – with $2.6 million spent on capital expenditure, $5.4 million on exploration and $1.2 million on expansionary studies.