ADULARIA (from the name of the Adula mountainous massif in the Switzerland * EN: adularia; DE: Adular; FR: adulaire, feldspath nacré; ES: adularia; RU: адуляр) is the mineral, morphological variation of the low-temperature orthoclase (Or).

The typical composition of the adularia corresponds to the formula Or90 Ab9 An1, where

Ab is the albite,

An is the anorthite.

The admixtures are: less than 1% BaO, not more than 0.5% CaO. It is found in the form of the short prismatic rhombohedron-like crystals. Adularia is typical for the numerous quartz veins of the alpine type, it is found in the pegmatites, and in the ore veins. The transparent and translucent adularia with the thinly-perthitic and the crypto-perthitic structure, having the iridescence in the light bluish and blue colours (the moonstone) is the gemstone of the IV order. Adularia is used in the glass and ceramic productive industries.