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Published online by Cambridge University Press: 14 March 2018
This unusual substitution appears to have taken place in a rock found by Mr. R. N. Worth, F.G.S., on Trowlesworthy Tor. The specimen was a loose block, and the rock to which Mr. Worth has given the name of Trowlesworthite has not yet been discovered in situ. The rock consists of red felspar, fluor-spar, and tourmaline, associated with quartz, and its general character and microscopic structure are described in papers published in the Transactions of the Royal Geological Society of Cornwall, Vol. X. p. 177.