Carrock Fell's geology is unique in the Lake District in that it is predominantly composed of Gabbro, a rough igneous rock that also makes up the famous Black Cuillin on the Isle of Skye. Gabbro is an excellent clean rock for climbers and Carrock Fell offers the only rock climbing of quality in the northern fells, the majority of which are made up of the unsuitable crumbly Skiddaw Slate. The fell is rich in mineral ores and has been mined extensively for many centuries with tungsten, lead, arsenic and iron all being extracted from the fell. The most famous mine on the fell was the Carrock Mine, the only source of tungsten in Britain outside of Devon and Cornwall. The mine was situated in Grainsgill Beck on the south western flanks of the fell with the main adit at a height of 340 metres. The mine was opened in 1854 but has only been worked in periods when the price of tungsten has been high, for example during wartime, the mine was worked extensively during both World Wars and the Korean War when supplies of Tungsten were threatened. The mine closed in 1981 and in 1988 the site was bulldozed and landscaped to its original outline.