Area: 0.6 hectare.

Description and Reasons for Notification: 

A new site, listed in the Geological Conservation Review as of national importance. 

One of the two mines in Britain worked commercially for uranium, this locality was also the site of subsequent radium extraction. Good samples of uranium secondary minerals and some pitchblende occur in the dumps opposite the adit mouth. Elsewhere, the uranium ores are often associated with nickel and cobalt and excellent samples of arsenides including rammelsbergite, smaltite, skutterudite, gersdorffite and lollingite can still be obtained from a small dump near south shaft. Other unusual minerals are bismutoferrite, bismuth, xanthiosite and aerugite, the last two being rare nickel arsenides only known from one other locality in the world. 

This site is of considerable interest for the variety of unusual and rare minerals contained in the mine dumps. These have been dated at 225 million years and 47 million years, representing two reworkings of original Hercynian crustal components found elsewhere in southwest England.