Amalgamation: Tregothnan United. Small mine that operated intermittently from 1800 to 1840. According to Dines, there were several shaft dumps spaced at intervals of 125 yards along a northeast trending line, which possibly followed a lode, although no mine plans are available.

In 1860, the mine was reopened as New Wheal Clifford, and in 1873, it underwent another attempt at revival under the name Tregothnan United Mines. However, both operations were limited to workings above adit.

Between 1862 and 1870, Wheal Prosper, as the mine was known during this period, produced a variety of minerals, including 311 tons of copper ore averaging 2.5% copper, 86 tons of black tin, and 209 tons of arsenic. Additionally, it yielded a significant quantity of blende.