Matrix of the Diamond

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	34	THE MATRIX OF THE DIAMOND

	It is very common to find the small perovskite crystals surrounding a large crystal of olivine, as if attracted to it. The following figures are examples of this peculiarity :—



	The perovskite crystals lie on the outer sides of the olivine crystal, as if a later growth. In the same manner perovskite is attached to the outer surface of serpentine pseudomorphs after olivine. Fig. 29 shows such a case, and shows also in the serpentinised olivine secondary rutile needles growing out of a grain of titanic iron, as already described under olivine. A similar grouping of small perovskite crystals, like a wreath, around the olivines has been noticed by Stelzner¹in the melilite-basalt of Hammerer Spitzberg, near Warten-berg, Bohemia (the so-called 'nephelin-pikrit' of Boficky),²which is rich in perovskite. Perovskite is one of the most characteristic minerals for the felspar-free basic eruptive rocks. As a rock ingredient it was first detected by Boricky³ in the above-named melilite-basalt of Wartenberg. Hussak⁴ proved its existence in the nepheline and leucite lavas of the Eifel; Stelzner⁵ showed that it was a constant constituent of melilite-basalts, and Sauer⁶ that it occurred very commonly in the nepheline and leucite-basalts of the Erzgebirge.

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