The northern part of this parish extends over the central mass of
granite, in the form of a long narrow stripe, the base of which is
about one mile north of the church. All the remainder of the parish
consists of compact and schistose felspar rocks, traversed by beds of
porphyry, and intersected by numerous veins of tin and copper, more
particularly of tin. On the whole, this parish bears a very close
geological resemblance to St. Austell.
See p. 401 of this Volume.