Brookite - Encyclopedia

    Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Orthorhombic
    Chemistry : TiO₂
    Rarity : Rare

Brookite is an accessory mineral that is typically found in the fissures of alpine-type gneisses and shales. It is also found in contact metamorphism zones, hydrothermal veins and is commonly found in alluvium. It is the rarest polymorph of TiO₂, the other two being rutile and anatase. It owes its name to the English mineralogist and crystallographer Henry James Brooke. The brookite is presented in centimetric lamellar crystals, strongly striated according to the elongation, much more rarely in prisms with vertically striated faces, terminated by pyramids. The brookite is transparent to opaque, of adamantine to metallic luster, and of yellow, brown-yellow, brown or black color. It is a mineral appreciated by collectors, some rare crystals have been cut as a gemstone.

In France, the Plan du Lac crystals (Isère) exceptionally reach 5 cm, however what is generally observed does not exceed one centimeter... while the Aiguille des Glaciers needles (Mont-Blanc) are famous for its acicular crystals of 3 cm.

The brookite would twinned on {120}, but uncertain...

No fake inventories for this mineral species, possible assemblies and re-bonding on certain pieces of Pakistan.