Brookite is a naturally occurring mineral composed of titanium dioxide (TiO₂) and belongs to the oxide mineral group. It is one of the three polymorphs of TiO₂, the other two being rutile and anatase. Brookite crystallizes in the orthorhombic crystal system and is known for its distinctive tabular or blade-like crystal forms. The mineral typically appears in colors such as brown, black, reddish-brown, or dark gray. In rare cases, it may also show yellow or even nearly colorless tones. Brookite crystals are usually opaque to translucent and exhibit a sub-metallic to adamantine luster. Although it can show some brilliance due to its high refractive index, it is not commonly used as a faceted gemstone.