anatasa

Anatasa (often spelled anatase in English) is a mineral form of titanium dioxide (TiO2) and one of the three naturally occurring polymorphs of TiO2, the others being rutile and brookite. Anatase crystallizes in the tetragonal system and is metastable, tending to transform to rutile at elevated temperatures.

Natural occurrence and formation: It occurs in a variety of geological settings, including hydrothermal veins and alteration zones of titanium-rich rocks, and as a weathering product of titanium-bearing minerals. It is widely distributed in nature and can be found as fine-grained crystals or in aggregates.

Physical properties: Anatase is typically colorless to pale brown and forms transparent to translucent crystals. It has a relatively high refractive index and a Mohs hardness around 5. Its density is about 3.9 g/cm3. It often occurs together with other TiO2 polymorphs in mineral deposits.

Industrial and technological significance: Anatase is one of the forms of titanium dioxide used in pigments. Although most commercial TiO2 pigments are rutile due to higher opacity and stability, anatase remains important for certain specialty pigments and for its photocatalytic properties. Anatase exhibits strong UV-induced photocatalysis, making it a focus of research for environmental cleanup, self-cleaning coatings, and solar energy applications. When heated, anatase can transform irreversibly to rutile.

See also: Rutile, Brookite, Titanium dioxide.