Beryl

Class: Silicates
Group: Beryl

Varieties | Names:

In granites and granite pegmatites, rarely in nepheline syenites. Also in mafic metamorphic rocks, low- to high-temperature hydrothermal veins and in vugs in rhyolite (Anthony et al., 2001—2005).

Heliodor — specimen 0426, photo © NMNHS

Original description: ‘Beril’ Vauquelin, L. N., 1798. Sur une nouvelle terre tirée de l’Aigue marine, ou Beril — Observations sur la Physique, sur l’Histoire Naturelle et sur les Arts 46: 158 [view in ‘Library’].

Type locality: unknown.

Type material: unknown.

Etymology: from the Greek βήρυλλος (beryllos); original significance unknown.

Distribution: Afghanistan: Panjshir Valley; Brazil: from Minas Gerais, around Téofilo Otoni and Itabira; Colombia: exceptional green crystals from the Muzo and Chivor districts; Madagascar: south of Antsirabe; Mozambique: Alto Ligonha district; Nigeria: near Jos; Pakistan: Skardu district, at Kunar; Russia: Mursinka, near Yekaterinburg, Urals, and from Nerchinsk, Siberia; USA: from the Pala district, San Diego Co., California; on Mt Antero, Colorado; at Hiddenite, Alexander Co., North Carolina; fine red crystals from Utah; Zimbabwe (Anthony et al., 2001—2005).

Chemistry

Be3Al2Si6O18

Essential elements: beryllium (Be), oxygen (O), aluminium (Al), silicon (Si).

Crystal data

Crystallography: hexagonal — dihexagonal dipyramidal. Crystal habit: crystals prismatic to tabular; may be complexly terminated by pyramids, to 18 m and 180 t (Anthony et al., 2001—2005).

Physical properties

Cleavage: imperfect on {0001} (Anthony et al., 2001—2005). Fracture: conchoidal to uneven (Arem, 1987: 52). Tenacity: brittle (Arem, 1987: 52). Hardness: 7.5—8 (Arem, 1987: 52). Density: 2.6—2.9 g/cm3 (Arem, 1987: 52). Luminescence: none.

Optical properties

Colour: colourless, white, pale blue to sky-blue, bluish green through green to greenish yellow or yellow, rose to peach, deep pink to raspberry-red; may be zoned; commonly colourless in thin section (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous, resinous (Anthony et al., 2001—2005). Refractive index: 1.56—1.604 — anisotropic [uniaxial (-)] (Lazzarelli, 2012). Birefringence: 0.003—0.01. Dispersion: 0.014. Pleochroism: weak to distinct; O = colourless, yellowish green, light blue, yellowish red; E = sea-green, blue, purplish red (Anthony et al., 2001—2005).

Material from ‘Repository’

39 specimens: 0245 — 1.29 ct, Brazil; 0523 — 1.44 ct, Pakistan; 0445 — 1.32 ct, Brazil; 0522 — 0.38 ct, no precise locality [Africa]; 0423 — 1.01 ct, Brazil; 0063 — 1.49 ct, Brazil; 0302 — 2.11 ct, Brazil; 0424 — 1.29 ct, Brazil; 0351 — 0.13 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0353 — 0.09 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0354 — 0.15 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0355 — 0.14 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0357 — 0.09 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0594 — 0.05 ct, Afghanistan, Panjshir, Panjshir Valley, 35.42639°N 69.83333°E; 0194 — 1.61 ct, Brazil; 0187 — 2.36 ct, no locality data; 0439 — 0.56 ct, Brazil; 0577 — 0.09 ct, Brazil; 0506 — 0.42 ct, Madagascar; 0059 — 0.66 ct, Madagascar; 0213 — 0.50 ct, Madagascar; 0527 — 0.44 ct, Brazil; 0022 — 2.44 ct, Brazil; 0428 — 0.68 ct, Brazil; 0497 — 0.55 ct, Brazil; 0483 — 1.76 ct, Brazil; 0526 — 0.54 ct, Brazil; 0426 — 0.50 ct, Brazil; 0529 — 0.49 ct, Brazil; 0520 — 0.45 ct, Brazil; 0507 — 0.55 ct, Brazil; 0295 — 1.12 ct, Brazil; 0343 — 0.91 ct, Brazil; 0482 — 0.84 ct, Brazil; 0524 — 0.25 ct, Brazil; 0555 — 0.40 ct, Brazil; 0015 — 0.83 ct, Brazil; 0422 — 0.83 ct, Brazil; 0528 — 0.35 ct, Brazil.

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