St Barbara says it will sell its mothballed Southern Cross gold mining operations to China's Hanking Gold Mining for $22.5 million in cash.

The sale comprises of the Marvel Loch underground mine, a 2.2 million tonne per annum processing plant and a portfolio of potential exploration leases.

St Barbara ceased mining and processing at Southern Cross late last year and put the operation on care and maintenance.

The sale is expected to settle late February or early March subject to Foreign Investment Review Board and other regulatory approvals.