Cuillin Cuillin The Cuillin ( or ') is a range of rocky mountains located on the Isle of Skye in Scotland. The main Cuillin ridge is also known as the Black Cuillin to distinguish it from the Red Cuillin (', known locally as Red Hills), which lie to the east of Glen Sligachan. The peaks of the Black Cuillin are mainly composed of gabbro, a very rough igneous rock which provides a superb grip for mountaineers; and basalt, which can be very slippery when wet. The rocks forming the ridge of the Black Cuillin (and outliers such Bla Bheinn) are dark
Geology of Skye Part of the magma chambers for the volcanoes are exposed at the surface as major intrusions of gabbro and granite. These coarse-grained igneous rocks are relatively resistant to erosion and now form the Cuillin hills. The Black Cuillin are formed of gabbro, which erodes to form the characteristically jagged outlines, although this is in large part due to the many minor intrusions, such as dykes and cone sheets that cut the gabbro. The Red Hills are formed of granite and have a more rounded topography. All pre-Quaternary rock types on the island are affected by a major swarm of dykes,