Sphene (sometimes called Titanite) is a mineral that comes in green, yellow, white, brown or black wedge-shaped crystals (sphene means wedge in Greek). It's chemical formula is CaTiSiO5, Calcium Titanium Silicate. Sphene has a hardness of 5-5.5, a specific gravity of 3.3 - 3.6, and a white streak.Source localites include: Pakistan, Italy, Russia, China, Brazil, Switzerland, Madagascar, the Tyrol (Austria), Canada (Renfrew County, Ontario) and the USA (California). As a gemstone, sphene is usually some shade of chartreuse and is highly prized for its exceptional dispersive power (0.051, B to G interval) which exceeds that of diamond. Unfortunately, brittleness and low hardness precludes appropriate use as a ring stone: sphene is more suited to pendants or brooches, or left unset as a collector's stone.