OR/15/053 Kisimul Castle

Everett, P A, Gillespie, M R and Tracey, E A. 2015. Provenance of building stones in four 'galley castles' in Argyll. British Geological Survey Internal Report, OR/15/053.

Kisimul Castle is located on a small island off Castlebay on the island of Barra in the Outer Hebrides. A single piece of decorative stone from Kisimul Castle was provided to BGS by Historic Scotland, and a thin section for petrographic analysis was prepared (see Appendix 1).

The sample is a thin tabular block, c.20 x 15 x 5 cm, of greyish-green metamafic rock. Thin section examination reveals that the rock has a very strong planar foliation suggesting it has been very strongly deformed to the extent that the constituent crystals have deformed in a plastic manner and have been drawn out in long ‘ribbons’ (the geological term for this type of texture is mylonitic). Zones of very strongly deformed rock (mylonite) are common on Barra, and much of the rest of the Outer Isles, and this decorative stone therefore is likely to have been sourced from an outcrop near to Kisimul Castle.