New Roskear Shaft, Dolcoath Mine, Tuckingmill, Carn Brea area, Camborne - Redruth - St Day District, Cornwall, England, UK

In 1920, when further exploration of the bottom levels of Dolcoath Mine became unprofitable, the mine was abandoned and attention was directed to the Roskear section to the north, which had been acquired by the West Dolcoath Exploration Syndicate around 1898. In 1929, New Roskear shaft was sunk to a depth of 2,000 feet between the North and South Roskear main lodes, in order to explore the ground below the copper ore zone of these mines where rich tin ores were believed to exist.

From the surface, the shaft passed through greenstone (dolerite) and killas. Below 300 feet, a dark massive hornfels was cut, and below 620 feet, more greenstone was encountered which was invaded by small veinlets with weak tin or sulphide mineralization. Below 870 feet, it passed into hornfels again which then continued to full depth. It was only crossed by two narrow aplite veins, a pegmatite vein carrying some garnet, a granite vein and an elvan dyke. Lode fragments encountered at depths above 1,600 feet carried mainly chalcopyrite and sphalerite. Tin-bearing lodes hit below and in crosscuts driven at depths of 1,700 feet, 1,900 feet, and 2,000 feet gave extremely irregular assay values; high grade mineralizations were only met sporadically. After this work was completed, further capital was needed. Though, the lodes opened up were not encouraging enough and the project was abandoned.

References:
- Dines, H.G. (1956): The metalliferous mining region of south-west England. HMSO Publications (London), Vol. 1, pp. 282-284.