V.—Note on an Olivine Gabbro (Forellenstein) from Cornwall

Extract

In Quart. Journ. Geol. Soc. 1877, pp. 906, et seq., Prof. Bonney describes a Gabbro from Coverack, on the eastern coast of the Lizard peninsula, which he remarks bears, macroscopically and micropically a close resmblance to the Forellenstein of Volpersdorf. I order to investigate further the nature the rock, I made, at his suggestion, an analysis of it. The piece selected had proved on microscopic examination to be almost free from pyroxenic constituents. No. I. was decomposed by fusion with alkalies. No. II. by hydrochloric acid. The residue in this case was white, and probably consisted of undecomposed felspar, showing that at any rate it was not all anorthite. No. III. is an analysis of the Volpersdorf rock quoted by Zirkel (Lehrb. der Petrog. ii. 139).