Titanite

Titanite, also known as sphene, is a calcium titanium silicate mineral with the formula CaTiSiO5. It forms in high-temperature metamorphic rocks and igneous rocks, particularly in calc-silicate skarns associated with granitic intrusions, as well as in metamorphosed limestones. Impurities and substitutions can produce color variations and affect optical properties.

In hand specimens, titanite crystals are typically yellow-brown to greenish-brown, though crystals can be colorless or pale. It is valued in part for its strong optical dispersion and pleochroism, which can give a bright fire in faceted gemstones. The mineral has a vitreous luster and a Mohs hardness of about 5 to 5.5, making it relatively soft for a silicate and prone to scratching. Titanite is relatively dense compared with many other silicate minerals.

Crystals are usually prismatic to tabular and can occur as well-formed crystals in granitic and skarn-rich rocks. The titanium content is a defining feature, and trace elements such as vanadium and iron influence color. The mineral is named for its titanium content; in the gem trade, it is commonly referred to as sphene when cut as a gemstone.

Titanite is distributed worldwide, with notable sources in countries such as Brazil, Sri Lanka, Norway, Canada, and Madagascar. It is primarily of interest to mineral collectors and as a source of gem-quality material, though its brittleness and relatively low hardness limit its use in some jewelry applications.