What is a perthite in geology ?
Perthite : definition
It is more precisely about exsolutions formed by cooling of a solid solution dominant orthoclase - albite. At high temperature K and Na are interchangeable and the compound of formula (K,Na)AlSi3O8 is single-phase; by cooling, this phase separates into two distinct and immiscible mineral phases : albite and orthoclase. Minority albite then appears in fine oriented inclusions : perthites.