Aeris Resources is nearing a decision on its Barbara copper project in North-West Queensland after the regulator granted a minor environmental authority amendment required to start mining.

The company said the feasibility study on the underground mining project was nearly complete, at which point it would be presented to the board for final investment decision.

It comes as the company’s Mount Colin copper mine in North-West Queensland winds down, with mining activities set to end in November.

Aeris took ownership of the mothballed Barbara site, 65km north-east of Mount Isa, in its $234 million takeover of Round Oak Minerals in 2022, which also brought Mount Colin into its portfolio.

The Barbara deposit supported an open-pit copper mine from March 2019 to December 2020, with sulphide ore crushed and trucked to Mount Isa for processing.

Aeris announced an updated mineral resource estimate last year of 2.2 million tonnes at 2.0 per cent copper and 0.2g/t gold for a total of about 45,000 tonnes of copper metal and 12,000 ounces of gold metal.

Related: Aeris kicks off feasibility study for Barbara underground

Aeris Resources executive chairman Andre Labuschagne told an investor forum the development timeframe for Barbara was driven by the approval process.

Having the required environmental authority amendment granted by the regulator meant the company could focus on the feasibility study, including getting quotes for contract mining, he said.

“… It will be a contract mining operation or we look at owner-operator as well as an option because we have the internal skills and equipment,” he said.

The company’s quarterly results presentation highlighted completion of the Barbara mining feasibility study and investment decision as a focus for the next quarter.

It reported declining mining rates at Mount Colin as the final stopes are taken.

Mined grade had improved quarter on quarter as more higher grade pillars were extracted, the company said.

A single processing run was completed last quarter at the Ernest Henry operation, although performance was poor.

A high proportion of low-grade oxidised material in the shipment resulted in low milled grade and metallurgical recovery, meaning metal produced was significantly below plan for the quarter, Aeris said.

At the end of the quarter, 175kt of stockpiled ore remained at EHM available for processing.

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