The company says it has undertaken ecology and archaeology studies

The Dartmoor Preservation Association and the Ramblers' Association want to stop the china clay company Imerys from using Crownhill Down.

The company has historic rights to mine at the site between Plymouth and Dartmoor.

A spokesman for Imerys says it has no intention of giving up the rights and the work in the area, but it will take into account the environmental concerns.

Any reasonable mineral operator today would obviously take into account these issues Ivor Bowditch, Imerys

Crownhill Down is outside Dartmoor National Park, but the land is considered by the conservationists to be of national park character.

The environmentalists argue that Crownhill Down is important for its wildlife, archaeology, landscape value and recreation purposes, and that any quarrying would destroy a beautiful and important area.

The Dartmoor Preservation Association in particular is calling for Imerys to give up its rights to quarry the area.

On Saturday, the first of a series of rallies will see walkers and riders converging on the Down from several directions in protest at the plans.

But Ivor Bowditch from Imerys said the work will take into account the environmentalists' concerns.

He said: "We have, in fact, already undertaken work to establish the ecology and archaeology of the area.

"I think that any reasonable mineral operator today would obviously take into account these issues, and we have that debate as publicly as we can with the mineral planning authority, which is Devon County Council."