On borolanite and its associates in Assynt

The previous section of this paper dealt with the spotted borolanites of Assynt, with special reference to the leucite question. Associated rocks were only mentioned in passing, as tending to throw light upon the affinities of the former group. It remains to undertake the systematic description of the rocks of the Borolan complex, and to indicate their genetic relationships. The subject may be treated under the following heads:— 1. The geological structure of the complex. 2. The petrology of the complex. 1. The differentiated rocks of the laccolite. 2. Dykes of the border zone. 3. Outlying dykes and masses. 3. The thrust rocks of the south-eastern tract. A. The Geological Structure of the Complex. The physical features of the district have been sufficiently described in earlier publications (I. p. 167; V. p. 428 et seq. ),1 and need only be briefly referred to. The centre of the complex is found in the hill Cnoc-na-Sroine which overhangs Loch Borolan. This hill shows more or less continuous exposures of igneous rock from near Ledbeg in the north-west to near Strathsheaskich in the south-east, and also from Loch Borolan to Ruighe Cnoc in the north-east (see map). The hill is completely surrounded by a fringe of peat bog, which largely obscures the lower rocks. The bog is dissected on the north and west by the Ledbeg River, and on the south-west side by the Ledmore River and some smaller streams, but within the water-logged area, there are practically no