The endangered ecological community is among 678 hectares of vegetation, identified in an environmental assessment report, that would be affected if the Coal & Allied expansion goes ahead.

With only 13 per cent, or 800 hectares, of the woodland remaining and fears that mining could make it extinct, residents have called for the woodland to be spared.

Mount Thorley resident Carol Russell said the unique vegetation, built on aeolian, or wind-driven, sands, could never be replaced.

"They could try to establish a woodland, but it won't be Warkworth Sands Woodland - not on mine spoil," she said.

"It's a very rare and unique woodland on very, very old sand.

"The whole of the Bulga, Warkworth area is concerned about it."

It is the latest threat to the Walkworth Sands Woodland.

In 2003, approval for a previous expansion of the mine paved the way for 35 hectares of the woodland to be cleared, but to date the clearing has not been done.

Coal & Allied said it contracted the University of New England (UNE) in 2008 to undertake a five-year research program into re-establishing species found on the wooded sands.

Research included soil seed reserves, germination trials and revegetation activities.

"We believe UNE's research work will have application for future offset areas," a Coal & Allied spokeswoman said.

But the mining company's Community Consultative Committee is yet to hear the program's progress, because a meeting with university researchers was cancelled last week.

The spokeswoman said Coal & Allied and the researchers were trying to set a new meeting date as soon as possible.