Geology

Essentially the surface of the South Crofty ‐ Dolcoath ‐ Roskear area is situated on "killas", a series of metasediments, hornfels and skarns, close to the granite contact (which crops out at surface a little to the north of the railway and is aligned ENE). In depth, the granite underlies the entire area but is encountered at increasingly greater depths northwards. The granite surface slopes NNW at angles of 40 to 50 degrees but has rolls and ridges, rather than being planar. It is thought that these local undulations may have some controlling influence or association with the localisation of mineralization. The Granite is that of the Carn Brea stock, which forms the prominent hills of Carn Brea, Carn Arthen and Carn Entral south of the mine site. A series of "greenstone", typically metadolerite, dykes and metabasite sills crop out to the north. Evidence of skarns, pegmatites, quartz floors and greisened areas have been disclosed but, to date, none have attained economic significance.

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