The company said coal reserves at the seam in the eastern side of the basin, which are currently quoted at 6.5Mt, could now be doubled, increasing total mine reserves at Duralie to more than 25Mt.

Gloucester Coal chief executive Gavin May said it was an exciting development for the company.

“We believe the discovery may double our current reserves in the east Duralie area and contribute substantially to extending the life-of-mine operations,” May said.

The company discovered the Clareval Seam, which features low-ash, high-fluidity coking coal, last December.

Drilling within the company’s existing Duralie mining lease has already found approximately 1Mt of coal amenable to shallow, opencut mining adjacent to the existing opencut mine.

“Importantly, this discovery gives further support to Gloucester Coal’s belief that with a focused exploration campaign, opencut mining operations could continue out to 2030,” May said.

Further exploration is scheduled for October/November following a review of environmental factors over the east Duralie drilling area.