Titanite

Titanite, also called sphene, is a calcium titanium silicate mineral found in igneous and metamorphic rocks. Its high refractive index and dispersion make transparent crystals prized as gemstones.

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Silicate minerals: Minerals built from silicon–oxygen tetrahedra, alone or combined with other elements. Titanite belongs to this broad mineral family through its silicate structure.
Refractive index: A measure of how strongly light slows and bends in a material. Titanite’s high refractive index contributes to its bright appearance when cut.
Gemstone: A mineral or other material cut and polished for use in jewelry or adornment. Transparent titanite is faceted for its brilliance and strong color dispersion.
Zircon: A zirconium silicate mineral valued as a gemstone and used in geochronology. Zircon can resemble titanite as a gem and also serves as a uranium–lead geochronometer.
Titanium: A chemical element with symbol Ti and atomic number 22. Titanium is an essential constituent of titanite’s chemical formula.
Dispersion (optics): The separation of light into wavelengths because a material refracts each wavelength differently. Strong dispersion gives faceted titanite conspicuous flashes of spectral color.
Uranium–lead dating: A radiometric dating method that uses uranium isotopes decaying into lead isotopes. Uranium-bearing titanite can provide ages for crystallization or later geological events.
Rutile: A titanium dioxide mineral occurring in many igneous and metamorphic rocks. Rutile is another common titanium mineral, but has a different composition and structure.
Calcium: A chemical element with symbol Ca and atomic number 20. Calcium occupies a major structural site in titanite.
Pleochroism: The appearance of different colors in a crystal when viewed along different directions. Some titanite crystals show direction-dependent colors that affect gem cutting.