Australian copper-gold producer Aeris Resources has kicked off the feasibility study for underground mining at the Barbara project, 65km north-east of Mount Isa.

The company provided an update in its quarterly report today, which also brought news that mining is expected to continue three months longer than planned at the Mount Colin mine in North-West Queensland.

Aeris said the feasibility study for the Barbara copper operation was expected to be completed in the first quarter of 2025.

The company this month submitted the environmental amendment paperwork for underground mining at Barbara.

Aeris took ownership of the mothballed Barbara site 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.

The deposit sits on an existing mining lease, significantly reducing the potential timeline to production.

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.

Extended mining timeline for Mount Colin

The company reported strong performance for the March quarter at Mount Colin, with production from the ‘cave’ zone in the upper levels of the mine going well.

‘Due to strong geotechnical performance of the upper levels of the cave and a revised mine design for pillar extraction, mining at Mount Colin will continue approximately three months longer than planned and into Q1 FY25,’ the company stated.

Related: Aeris raising $30m amid Mount Colin revenue delays

At the end of the quarter, mined ore stockpiles at the Mount Colin mine and the toll processing plant totalled 168kt (more than one quarter of mining). A further processing run of 105kt was completed in mid-April.

Aeris said there were no further processing runs scheduled in FY24 and, as a result, copper production for FY24 was forecast to be below guidance.

‘At the end of FY24, ore stockpiles of approximately 200kt grading 2 per cent copper available for processing are forecast. Processing runs have been scheduled in quarters 1 and 2 in FY25.’

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