titanit

Titanit, also called titanite, is a mineral species in the titanate-silicate group with the chemical formula CaTiSiO5. It is a calcium titanium silicate that crystallizes in the monoclinic system. Titanit is commonly found in igneous and metamorphic rocks as an accessory mineral and is notable for its variable color, typically yellow-brown, olive green, or gray, and for its adamantine to resinous luster.

Crystals of titanit are commonly elongated prisms and may be etched or twinned. It has a Mohs hardness of about 5 to 5.5 and a specific gravity around 3.4 to 3.5. Titanit is transparent to translucent and possesses strong optical properties, including notable birefringence, which makes it attractive as a gemstone variety known as sphene.

In jewelry, sphene is valued for its high dispersion and fire, though titanit is relatively soft and can be brittle, limiting its durability. The gemstone form is usually cut into small faceted stones or cabochons.

Geologically, titanit forms in a range of settings, most commonly in granitic and high-temperature metamorphic rocks, and may occur within skarns at contact zones. It can accommodate rare-earth or yttrium substituents, and its presence can help interpret metamorphic conditions and rock history.

Titanit is widely distributed worldwide, with notable occurrences in Europe, North America, Africa, and Asia. The name titanite reflects its relation to titan elements (calcium and titanium), while the gemstone variety remains marketed as sphene in the jewelry trade.