Isomorphous series of feldspars ranging in composition between albite (NaAlSi₃O₈) and anorthite (CaAl₂Si₂O₈). Between the two end-members there is a continuous solid solution series: albite, oligoclase, andesine, labradorite, bytownite, anorthite. Usually, the higher the temperature of formation the more likely the feldspar is to be calcium-rich, whereas at lower temperatures sodium-rich plagioclase tends to form. The preservation of electrical neutrality in the plagioclases is achieved by concomitant substitution of Ca²⁺ and Al³⁺ by Na⁺ and Si⁴⁺. See plagioclase feldspar.