n.
Any member of the series of abundant feldspar minerals that usually occur as light-to medium-grey-coloured, transparent to translucent grains or crystals.
Plagioclase ranges in composition from albite to anorthite . It is used in the manufacture of glass and ceramics; iridescent varieties are valued as gemstones. The primary importance of plagioclase, however, derives from its role as a rock-forming mineral.