Description
The mineral series plagioclase (Ancient Greek: πλάγιος (plágios), to solid and κλάσις (klásis), to break, fracture) is a group of aluminium-tectosilicates belonging to the feldspars with endmember compositions intermediate between albite and anorthite, with albite as the sodium-bearing and anorthite as the calcium-bearing outermost mineral. The mineral series is a so-called solid solution. Albite – NaAlSi3O8 Oligoclase, Andesine, Labradorite, Bytownite,Anorthite – CaAl2Si2O8 The crystallography of the feldspars varies strongly with composition and is quite complex. The symmetry ranges from monoclinic to triclinic. In general, multiple cleavage systems exist, and high- and low-temperature forms also exist. The individual plagioclase minerals, commonly abbreviated as plagioclase, are important rock-forming minerals in felsic igneous, metamorphic, and sedimentary rocks. A common color of plagioclase crystals is milky white, making it a relatively easy mineral to recognize in rocks.
