An abundant rock-forming mineral typically occurring as colourless or pale-coloured crystals and consisting of aluminosilicates of potassium, sodium, and calcium.‘Quartz is associated most commonly with aegirine and potassium feldspar as well as zircon.’
- ‘Larger crystals of feldspar and quartz dominate the host rock.’
- ‘These granite dikes are composed almost totally of potassium feldspar and quartz.’
- ‘Minerals such as feldspar, which are insoluble in water, will not give a positive test.’
- ‘Its most abundant mineral is feldspar, which accounts for two-thirds of the Earth's crust.’
Mid 18th century alteration of German Feldspat, Feldspath, from Feld ‘field’ + Spat, Spath ‘spar’ (see spar). The form felspar is by mistaken association with German Fels ‘rock’.