Muckish meaning "the pig's back" forms part of the Derryveagh Mountains. It is 666 metres high, and is the 163rd highest in Ireland. It is also the most northern and second highest of the mountain chain called the "Seven Sisters". The Seven Sisters includes: Muckish, Crocknalaragagh, Aghla Beg, Aghla More, Ardloughnabrackbaddy, Mackoght and Errigal. High-grade quartz sand was mined on the flanks of the mountain, The sand was exported and was mainly used in the manufacture of optical glass.