Plagioclase Wikipedia
Plagioclase displaying cleavage. (unknown scale) In volcanic rocks, finegrained plagioclase can display a "microlitic" texture of many small crystals. Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more ...