ANORTHITE (from the Greek word "anorthos" (oblique), according to the oblique shape of crystals * EN: anorthite, calciclase; DE: Anorthit; FR: anorthite; ES: anortita; RU: анортит) is the rock-forming mineral, the end member of the isomorphous series of plagioclases, Ca[Al2Si2O8]. They refer to anorthites the basic end members of the series, which are containing 90-100% (molecular) of the anorthite component. It crystallizes into the triclinic crystal system.

The crystals of anorthite are rare, there are common the separate grains and granular aggregates. Often there have the same composition, as anorthites, the central parts of the zonal phenocrysts of plagioclase (within the effusive rocks), and of the plagioclase grains (within the certain basic intrusive rocks). The colour is white, gray, greenish; sometimes blue or pink (because of the mechanical inclusions of other minerals). The hardness is 6-6.5; it is brittle. The density is 2750±10 kilograms per cubic metre.

It is mainly the magmatic mineral. It may be found within the basic effusives, sometimes also within the basic intrusive rocks of the group of gabbro (olivine norites, certain anorthosites of the layered intrusions, and others); it has been noted within the pyroxenic hornfels. Together with other plagioclases, it is the major constituent of concentrates, which are used in the ceramic industry. It is beneficiated by flotation, with preliminary extraction of micas and quartz from the ores; the collectors are cationic, and petroleum oils; the activator is the processing with NF, the depressors are the salts of Ca, Ba, Mg.