Amalgamated alongside Wheal Cupboard and Poldory into United Mines around 1780. United Mines continued to expand and became a rival to neighbouring Consolidated Mines. In 1857 the two joined to become Clifford Amalgamated Mines. Closed circa 1870.
A great many of the mine pumps and engines of the area were installed by Richard Michell (1748–1836, aged 89) of Gwennap, son of Thomas Michell manager of the Polgooth Mine (St Austell, 1740 to 1757).
The Boulton & Watt Correspondence and Papers, 1769-1895 held at the library of Birmingham show correspondence between Thomas and Richard Michell and Boulton & Watt. One document describes an engine with a 58 inch cylinder and 9 feet stroke.
