Plagioclase refers to a group of feldspar minerals that exist in solid solution between Albite (NaAlSi3O8) and Anorthite (CaAl2Si2O8) endmembers. The range of minerals include Albite, Oligoclase, Andesine, Labradorite, Bytownite, and Anorthite. Each mineral represents a specific composition between albite and anorthite. It is a major component of the Earth's crust.