Albita

Albita is a mineral belonging to the plagioclase feldspar series. It is the calcium-rich endmember of this solid solution series, with a chemical formula of NaAlSi3O8 to CaAl2Si2O8. Pure albite has the ideal formula NaAlSi3O8, while the pure calcium endmember is anorthite, CaAl2Si2O8. Albite minerals contain varying proportions of sodium and calcium, with albite considered to be plagioclase with less than 10% anorthite content. It is a common constituent of many igneous and metamorphic rocks.

Albite typically occurs as colorless to white crystals, often appearing as glassy grains. It is a relatively soft mineral, with a Mohs hardness of 6 to 6.5. Its specific gravity ranges from approximately 2.62 to 2.65. Albite can be found in a variety of geological settings. It is a primary mineral in felsic igneous rocks such as granite and rhyolite, and also appears in some mafic rocks. In metamorphic environments, albite is a key component of blueschists and greenschists. It can also be found in pegmatites and hydrothermal veins.

Distinguishing albite from other plagioclase feldspars can be challenging without detailed analysis. Macroscopically, it often appears as white to gray or colorless masses. Common twinning in albite includes albite twinning, which often produces characteristic striations on crystal faces, and Carlsbad twinning. These twinning features are important diagnostic characteristics used in mineral identification.