Brookite

Brookite

Formula: TiO₂

Mohs scale hardness: 5,5–6

Specific gravity:4,08-4,18

Brookite is the orthorhombic variant of titanium dioxide, TiO₂, which occurs in four natural polymorphic forms (minerals with the same composition but different structure).

Arkansite is a variety of brookite from Arkansas, USA.

Crystals are typically tabular, elongated and striated parallel to their length. Brookite is usually brown in color, or sometimes yellowish or reddish brown, or even black. Beautiful, deep red crystals similar to pyrope and almandite garnet are also known. Brookite is a brittle mineral.

Brookite is an accessory mineral in alpine veins in gneiss and schist; it is also a common detrital mineral. Associated minerals include its polymorphs anatase and rutile, and also titanite, orthoclase, quartz, hematite, calcite, chlorite and muscovite.