Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is (Ca, Na)(Al, Si)₄O₈, where Ca/(Ca + Na) (% Anorthite) is between 30%-50%. The formula may be written as Na_0.7-0.5Ca_0.3-0.5Al_1.3-1.5Si_2.7-2.5O₈.