Uvite

Class: Silicates
Group: Tourmaline

Typically in calcium-rich rocks subjected to contact metamorphism and metasomatic processes which added boron (Anthony et al., 2001—2005).

Uvite — specimen 0030, photo © NMNHS

Original description: Henry et al., 2011. Nomenclature of the tourmaline-supergroup minerals — American Mineralogist 96: 895—913 [view in ‘Library’].

Type locality: Brumado, Bahia, Brazil.

Type material: Geological Survey of Canada, Ottawa, Canada, 13320; Harvard University, Cambridge, Massachusetts, 116455; Natural History Museum, London, England, 1976, 426; National Museum of Natural History, Smithsonian Institution, Washington, DC, USA, C3283, C3287, C5212; Royal Ontario Museum, Toronto, Canada (Anthony et al., 2001—2005).

Etymology: named for Uva Province, Sri Lanka.

Distribution: Brazil: Brumado, Bahia; Myanmar; Sri Lanka: Uva Province; USA (Anthony et al., 2001—2005).

Chemistry

Ca(Mg3)MgAl5(Si6O18)(BO3)3(OH)3(OH)

Essential elements: hydrogen (H), boron (B), oxygen (O), magnesium (Mg), aluminium (Al), silicon (Si), calcium (Ca).

Crystal data

Crystallography: trigonal — ditrigonal pyramidal. Crystal habit: crystals prismatic, pyramidal, to 15 cm; cross sections are typically triangular with curved, convex sides (Anthony et al., 2001—2005).

Physical properties

Cleavage: no data. Fracture: uneven to conchoidal (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 7.5 (Anthony et al., 2001—2005). Density: 2.97—3.14 g/cm3 (Anthony et al., 2001—2005). Luminescence: may fluoresce weak yellow under SW UV (Anthony et al., 2001—2005). Other: pyroelectric and piezoelectric (Anthony et al., 2001—2005).

Optical properties

Colour: brown, light to dark green, red , black (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous to resinous (Anthony et al., 2001—2005). Refractive index: 1.614—1.666 — anisotropic [uniaxial (-)] (Anthony et al., 2001—2005). Birefringence: 0.014—0.032. Dispersion: 0.017. Pleochroism: O = pale yellow; E = colourless (Anthony et al., 2001—2005).

Material from ‘Repository’

1 specimen: 0030 — 0.18 ct, Canada, Ontario, Haliburton County, Irondale, Salerno Lake.

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