Class: Silicates
Group: Rhönite
Original description: Prior, G. T., Coomáraswámy, A. K., 1903. Serendibite, a new borosilicate from Ceylon — Mineralogical Magazine 13: 224—227 [
view in ‘Library’].
Type locality: Gangapitiya, Ambakotte, Central Province, Sri Lanka.
Type material: unknown.
Etymology: after Serendib, the old Arabic name for Sri Lanka.
Distribution: Canada: on the Melville Peninsula, Northwest Territories; Madagascar; Russia: Sakha Republic; Sri Lanka: Gangapitiya; Tanzania; USA (
Anthony et al., 2001—2005).
Chemistry
Ca2(Mg,Al)6(Si,Al,B)6O20
Essential elements: boron (B), oxygen (O), magnesium (Mg), aluminium (Al), silicon (Si), calcium (Ca).
Crystal data
Crystallography: triclinic — pinacoidal.
Crystal habit: rarely in small tabular crystals; as anhedral grains, to 2 cm, and aggregates.
Twinning: polysynthetic on {011}, common (
Anthony et al., 2001—2005).
Optical properties
Colour: greyish blue-green to deep blue, green, or brown; in transmitted light, nearly colourless to pale yellow-green or blue (
Anthony et al., 2001—2005).
Diaphaneity: transparent (
Anthony et al., 2001—2005).
Lustre: vitreous (
Anthony et al., 2001—2005).
Refractive index: 1.696—1.702 — anisotropic [biaxial (-)] (
Lazzarelli, 2012).
Birefringence: 0.05.
Dispersion: no data.
Pleochroism: strong; X = pale yellow, yellow-green to blue-green; Y = almost colourless, pale yellow, blue, blue-green; Z = light to dark blue (
Anthony et al., 2001—2005).
Material from ‘Repository’
2 specimens: 0438 — 0.48 ct, Myanmar, Mandalay, Mogok, 22.930097°N 96.515206°E;
0437 — 0.58 ct, Myanmar, Mandalay, Mogok, 22.930097°N 96.515206°E.
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