Description
Brookite is the orthorhombic form of titanium dioxide (TiO2), which occurs in four known natural polymorphic forms (minerals with the same composition but different structures). The other three of these forms are akaogiite (monoclinic), anatase (tetragonal), and rutile (tetragonal). Brookite is rare compared to anatase and rutile and, like them, exhibits photocatalytic activity. [Brookite also has a larger cell volume than anatase or rutile, with 8 TiO2 groups per unit cell, compared to 4 for anatase and 2 for rutile. Iron (Fe), tantalum (Ta), and niobium (Nb) are common impurities in brookite. Brookite was named in 1825 by the French mineralogist Armand Lévy [for Henry James Brooke (1771–1857), an English crystallographer, mineralogist, and wool merchant. Arkansite is a variety of brookite from Magnet Cove, Arkansas, USA. It is also found in the Murun Massif on the Olyokma-Chara Plateau in eastern Siberia, Russia, part of the Aldan Shield. At temperatures above about 750°C, brookite reverts to its rutile structure
