A GREEN group hopes the discovery of a rare rock formation could help their fight against opencasting.

Tufa has been discovered in Pikewell Burn, which feeds into Pont Burn, at Dipton, near Stanley, County Durham.

It is formed from deposits of calcium left by stream water and leads to the creation of little waterfalls.

It is rare in the North-East and more commonly found in limestone areas rather than coal-bearing areas. Samples from the burn are currently being tested.

The Pont Valley Network, a local group dedicated to the area’s conservation, wants it to be declared a Site of Special Scientific Interest (SSSI).

The group was among the opponents of a big opencast site at nearby Bradley, which will be the subject of a second public inquiry later this year.

It hopes SSSI status would make it harder for such developments to take place.

Network chairman David Marrs said: “The most rare thing is it shouldn’t be here . Because Tufa is calcium it should be in limestone, not in a coal measures, area so there is something strange that is happening that this Tufa is appearing in this burn.

“Tufa is incredibly fragile. It is calcium-rich water that deposits on plants and forms this rock. It forms little waterfalls across the burns. There are over 80 or 90 of them.

“These little waterfalls are less than 1,000 metres from the opencast site and there is obviously water running underground between them.’’ A spokeswoman for Natural England said the presence of Tufa would not be a sole reason for SSSI status.

She added: “There is an England-wide review of Tufa sites taking place and they are well aware of Pont Burn.

“That will happen sometime this financial year and they should end up with a shortlist of geological conservation review sites.

“They in turn will be reviewed and ratified by other agencies and would then be considered for notification as an SSSI.

“We are talking about 2016-2017 for that whole process to be completed.’ “A designation of SSSI gives a site protection from development.”