Feldspar is the most abundant mineral group in Earth’s crust and commonly forms pink, white or gray crystals in igneous rocks.
Feldspars are aluminium silicate minerals containing potassium, sodium or calcium. The group is divided mainly into alkali feldspars, such as orthoclase and microcline, and plagioclase feldspars, which form a compositional series between sodium-rich albite and calcium-rich anorthite.
Their abundance reflects the composition of Earth’s crust and the way common magmas crystallize. Granite often contains conspicuous pink or white feldspar, while basalt commonly contains small plagioclase crystals. Feldspar also weathers readily to form clay minerals, contributing important material to soils and sediments.
Feldspar is a mineral group rather than one single mineral species. This matters because color alone cannot reliably identify a particular feldspar: quartz, for example, may look similar but has different cleavage and chemistry.