Pelitic gneiss and schist of predominantly Mesozoic age crop out on the east side of Harrison Lake. Locally, members of the Cretaceous and/or Tertiary Custer Gneiss are extremely pelitic and may contain up to 50 per cent garnet (averaging approximately 20 per cent) and up to 40 per cent coarse-grained kyanite (averaging approximately 15 per cent) (Reamsbottom, 1971; 1974). Members of the Slollicum Schist and Settler Schist are also locally pelitic, containing from 4 to 50 per cent garnet, with averages of approximately 10 to 15 per cent, minor kyanite or andalusite and from 0 to 35 per cent sillimanite (Reamsbottom, 1971; 1974).