The Kanmantoo copper mine may stay open for years longer than expected if digging can continue underground, Hillgrove Resources has announced.
When it reopened in 2012, the resources being mined there were expected to last only until this year.
But at Hillgrove's annual general meeting on Thursday, the board told shareholders a "very significant" copper and gold deposit existed beneath and in one wall of the main pit, which is already projected to reach a depth of 350 metres.
Exploratory drilling will begin late this year if funding permits.
The company is also excited about another deposit, named Kanappa, 44 kilometres up the range at Sanderston.
Analysis of soil, rocks and magnetic imagery indicated a high grade of copper was likely present over an area of about two square kilometres.
The company plans to drill exploratory holes there, too, by the end of the year if possible.
Hillgrove Resources employs almost 250 people at Kanmantoo and mines up to 20 million tonnes of ore, producing 20,000t of copper, each year.
Outgoing chairman Dean Brown reported that the company was better placed than a year ago, when it reported a range of financial problems to the Australian Stock Exchange.
"By the end of 2017, I expect Hillgrove to be in a stronger financial position underpinned by a much-improved balance sheet and with a focus on growth," he said.
The Kanmantoo copper mine originally operated between 1846 and the 1970s.