Uvite
CaMg3(Al5Mg)(BO3)3Si6O18(OH)3(OH,F)
A calcium-magnesium tourmaline that forms in metamorphosed limestones, typically dark green to brown and often in well-formed crystals.
- Mohs hardness
- 7-7.5
- Color
- Brown, dark green, black, yellow-green
- Type
- mineral
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Overview
Uvite is a calcium- and magnesium-rich member of the tourmaline group, closely allied to dravite but with calcium replacing sodium in the structure. The fluorine-bearing variant fluor-uvite is common. It was named in 1929 after the Uva Province of Sri Lanka.
Unlike the lithium tourmalines of granite pegmatites, uvite is a hallmark of calcium-rich metamorphic settings, especially marbles and skarns. It commonly occurs as sharp, lustrous crystals that make excellent collector specimens.
Colors range from rich brown and yellow-green to deep green and black, depending on iron, magnesium and titanium content.
Formation & geology
Uvite forms during regional and contact metamorphism of impure, dolomitic or magnesian limestones. Boron introduced by metamorphic fluids reacts with the calcium and magnesium of the carbonate host to crystallize tourmaline within marble and skarn.
It is frequently found alongside calcite, diopside, phlogopite and other calc-silicate minerals. Well-developed crystals can be etched free of their carbonate matrix when the calcite is dissolved.
Notable localities include Brumado in Bahia, Brazil (famous for fine green and brown crystals), the marbles of Sri Lanka, the United States, and various Alpine and metamorphic terrains.
How to identify it
Uvite forms prismatic to stubby crystals, often with flat terminations and the curved-triangular cross-section common to tourmaline. It is hard (7-7.5), has a vitreous luster, white streak and no cleavage.
Color is usually brown to dark green, which can resemble dravite, schorl or even some garnets. Its association with marble and calc-silicate minerals is a strong contextual clue, and definitive separation from dravite requires chemistry showing calcium dominance.
Strong pleochroism and lengthwise striations help confirm it as a tourmaline rather than a look-alike like epidote or vesuvianite.
Uses & significance
Uvite is mainly a collector and specimen mineral; sharp, lustrous crystals from localities like Brumado are highly sought. Transparent green or brown material is occasionally faceted into gemstones for collectors.
It has little industrial use, though tourmaline-group minerals collectively are studied for their boron content and as indicators of metamorphic fluid conditions.
As with all tourmalines, metaphysical sellers attribute grounding and protective properties, but these are not scientifically supported.
Frequently asked questions
How is uvite different from dravite?
Both are magnesium-rich tourmalines, but uvite is calcium-dominant while dravite is sodium-dominant; lab analysis is needed to distinguish them.
Where does the best uvite come from?
Brumado in Bahia, Brazil, is renowned for superb green and brown uvite crystals, with other occurrences in Sri Lanka and the United States.
Is uvite a gemstone?
Transparent crystals can be faceted, but most uvite is valued as collector specimens rather than mainstream jewelry stones.
What rock does uvite form in?
It typically forms in metamorphosed limestones and dolomites, growing in marble and skarn with calcite and calc-silicate minerals.
Uvite guides
In-depth guides for identifying, valuing, and understanding Uvite.
