Their outcrop extends in a belt of variable breadth from Cape Wrath to the Point of the peninsula of Sleat in Skye, running in a N.N.E.-S.S.W. direction through Caithness, Sutherland, Ross and Cromarty, and Skye and Lochalsh. They form the isolated mountain peaks of Canisp, Quinag and Suilven in the area of Loch Assynt, of Slioch near Loch Maree, and other hills. They attain their maximum development in the Applecross, Gairloch and Torridon districts, form the greater part of Scalpay, and occur also in Rùm, Raasay, Soay and the Crowlin Islands. They are also found beneath much of the Sea of the Hebrides overlying the Lewisian gneiss.