What is "andesine"

Andesine \An"des*ine\, n. (Min.) A kind of triclinic feldspar found in the Andes.

n. (context mineral English) sodium calcium aluminum silicate, ($Na\_xCa\_xAlSi\_3O\_8$), a plagioclase feldspar, the third member of the albite-anorthite solid solution series. Found in fine-grained andesite lavas; crystals are rarely seen.

Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is ( Ca, Na)( Al, Si) O, where Ca/(Ca + Na) (% Anorthite) is between 30%-50%. The formula may be written as NaCaAlSiO.

The plagioclase feldspars are a continuous solid solution series and as such the accurate identification of individual members requires detailed optical study, chemical analysis or density measurements. Refractive indices and specific gravity increase directly with calcium content.