a plagioclase containing more sodium than calcium, occurring in light gray, yellow, or greenish crystals. [AHDOS
(Also called Plagioclase) A triclinic feldspar made of soda- lime.
Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite (NaAlSi3O8) and anorthite (CaAl2Si2O8). The albite : anorthite molar ratio ranges from 90 : 10 to 70 : 30.
