An extensive group of post-medieval bell pits was discovered during field survey in the 1980s. They cover an area of about 300m square and vary in size, shape and depth. On average they measure 5.7m across and between 0.7m and 1.5m deep. Around the pits are banks of spoil, sometimes forming a circle around the pit and sometimes a crescent-shape on the downslope side. The pits are closely spaced, sometimes with as little as 2.5m between them. Some of the pits are only shallow scoops and may show unfinished workings. They were probably dug for coal extraction.