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IN my paper on the Lizard this rock is mentioned, but without a specific name, for I had not then seen the figure given in 1898 by Rosenbusch (Elemente der Gesteinslehre, 1898, p.51). He calls it Beerbachite, and describes it on p. 219 as one of his Ganggesteine, among those von malchitischem Habitus, quoting an analysis. The name appears to have been given by Chelius to a rock from Frankenstein in the northern Odenwald, where it forms small veins in a gabbro, and has the following analysis: SiO2 = 47·21, Al2O3 = 20·52, Fe2O3 = 7·48, FeO = 5·32, MgO = 4·16, CaO = 8·63, Na2O = 5·17, K2O = 0·33, H2 = 0·34, P2O5 = 0·46, with 0·19 FeS2 and 0·10 hygroscopic water. He states that the rock is fine-grained to compact, not lustrous, grey to pale grey in colour, consisting of a panidiomorphic mixture of labradorite and diallage, with a variable amount of hypersthene and magnetite, and that olivine-bearing varieties occur. In these commonly a brown hornblende replaces the diallage, in which the above-named constituents are pæcilitic. He states that beerbachite also occurs in gabbro near Harzburg and in the Isle of Mull.
page 339 note 1 I studied the coast north of Crousa Down, from St.Keverne, in 1890, with my friends General McMahon and Canon Hill, and again in 1894 with the latter. I revisited it in 1908. when staying with Dr. Flett at Kennack Cove, to discuss sundry points on which we were not agreed, but do not remember that we used then the word beerbachite; and have since seen a little of the neighbourhood in 1909 and 1912.
page 340 note 1 These, as a rule, are not welded to the gabbro, beerbachite, or serpentine, as the troktolite is to the last-named, so I regard the beerbachite as the forerunner of the “greenstone” (basaltic) dykes so common on the eastern coast of the Lizard.
page 340 note 2 See the analysis quoted in Rosenbusch's Gesteinslehre and Flett & Hill's Geology of the Lizard, etc.