I.—On Nepheline-Syenite and its Associates in the North-West of Scotland

Abstract

In 1892 I described, in conjunction with my colleague Mr. Horne, a peculiar rock, essentially composed of orthoclase and melanite, under the name of borolanite. The type-specimens came from the plutonic mass which lies to the north of Loch Borolan, in Sutherlandshire (1 in. sheet 101). During the preparation of the paper on borolanite our colleague Mr. Gunn discovered two dykes of a closely related rock traversing the Torridon Sandstone in the Coigach district of West Ross-shire. The rock of these dykes was described in an appendix to our paper. It contains nepheline and ægirine, in addition to orthoclase and melanite, and is therefore allied, both as regards mode of occurrence and mineralogical composition, to the Tinguaite group of Rosenbusch; but as melanite is an important constituent it was classed with the borolanites.