Archaeologists have dated these circles to the Late Neolithic or Early Bronze Age, and have noted that they are comparable to the stone circles found further south, on Dartmoor. In contrast to the two known Exmoor circles, over seventy such monuments have been identified on Dartmoor. This may be because Exmoor, unlike Dartmoor, has no natural granite. Instead it has Devonian slates and Hangman Grits, both of which easily break up into small slabs, resulting in a general shortage of big stones on Exmoor.