What is Uvite?
Uvite is a calcium-magnesium-aluminium tourmaline species, usually brown to green, valued for its chemistry, striated prisms and associations with metamorphosed carbonate rocks.
Mineralogy and structure
Reference formula: CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)4. Uvite is one of the principal tourmaline species and commonly forms compositional series with dravite and feruvite. Its existing Tourmaline relationship and published labelled representative COD structure are preserved. Uvite is classified with silicates and has trigonal crystal symmetry. Typical hardness is 7–7.5 on the Mohs scale and specific gravity is approximately 3.1–3.4.
Colour, lustre and habit
Typical colours include brown, yellow-brown, green, black, yellow. The usual prismatic, striated, granular habit and vitreous, resinous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Uvite forms in or is associated with marble, calc-silicate rocks, metamorphosed limestones and hydrothermal environments. Important documented localities include Sri Lanka, Italy, Brazil, Madagascar, the United States and Canada.
A calcium-magnesium tourmaline from altered marble
Uvite adds an important species-level link between gem tourmaline and metamorphic geology. Brown and green crystals are collected for sharp form, locality and the chemical story recorded by the host marble.
Collecting and care
Protect crystal terminations from impact and clean gently with mild water. Avoid acids, harsh heat and abrasive cleaning; document composition when a specimen is sold as a named species.
