Very old workings in Ausewell Wood above the river Dart, thought to be over a century old when visited in 1725.
Two parallel lodes of iron and copper extend through and alongside the rock and were developed here by open cast working and underground mining. The Cleft Rock itself (which appears is on current Ordnance Survey maps by this name) is a deep gunnis splitting the rock in two.
Locally pronounced as "Azel", the mine, then idle, was advertised for sale as Haswell Mine in 1763 and two years later, in 1765, appears on a map as the Hazel Mine. Workings at this time were from adit and shaft.
References:
Hamilton Jenkin, A.K. (1981): The Mines of Devon : North & East of Dartmoor, Devon Library Services : Exeter.
Newman, Phil. (2003): Ausewell Wood, Ashburton, Devon: Ausewell Mine (Wheal Hazel), Archaeological investigation report series, English Heritage, English Heritage.