The Term “Crinanite”

Abstract

The name crinanite was given in 1911 by Sir John Flett to a suite of N.W. analcite-dolerite dykes occurring in a fairly extensive district in Argyllshire of which Loch Crinan is the centre. A description of the type is accompanied by an analysis and a photomicrograph of a characteristic example from the island of Jura. Writing a few months later of similar dykes in Colonsay, the same author gives a concise definition of the type—“The crinanites, then, are dark coloured, fine-grained, basic rocks consisting mainly of olivine, augite, and plagioclase felspar, with a considerable amount of analoite and zeolites.” A detailed description follows, in which the very perfect ophitic structure of the rocks is emphasized, and another excellent photomicrograph is shown of an example from Colonsay. In his original description Sir John Flett states that the crinanites “present some analogies to the teschenites in mineral composition; from the latter they are distinguished by their finer grain, their perfect ophitic structure, the scarcity of hornblende and biotite, and their occurrence as thin vertical parallel dykes”.