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Class: Oxides & hydroxides

Varieties | Names:

Characteristic of some granite pegmatites associated with mica schists or reaction zones in ultramafic rocks (Anthony et al., 2001—2005). The largest faceted specimen is a 245 carat oval from Sri Lanka (Arem, 1987: 67).

Original description: ‘Krisoberil’ Hoffmann, C. A. S., 1789. Mineralsystem des Herrn Inspektor Werners mit dessen Erlaubnis herausgegeben von C. A. S. Hoffmann — Bergmannisches Journal 1: 373, 387 [view in ‘Library’].

Type locality: [Brazil] ‘Brasilien’ (Hoffmann, 1789: 387).

Type material: unknown.

Etymology: derived from the Greek words χρυσός (chrysos) and βήρυλλος (beryllos), meaning golden, in allusion to the minerals colour, and beryl.

Distribution: widespread, notable localities include: Brazil: Bahia, Campo Formoso, Teixeira de Freitas, and Cachoeira; Espirito Santo: Tancredo, Colatina; Minas Gerais, Faria Lemos, and Americana, Teófilo Otoni; Madagascar: near Lake Alaotra, northeast of Ambatosoratra; Russia: Izumrudnye mines, Tokovaya River, near Yekaterinburg (Sverdlovsk), and Mursinka, Ural Mountains; Sri Lanka: Ratnapura district; USA: Colorado, Jefferson Co., near Golden; Maine, at Topsham, Paris, and Hartford, Oxford Co., and elsewhere; Zimbabwe: near Masvingo (Fort Victoria) (Anthony et al., 2001—2005).



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

Crystal data

Crystallography: orthorhombic — dipyramidal. Crystal habit: crystals are tabular on {001} or short prismatic along [100], to 22 cm; prominently striated on {001} || [100]. Twinning: common on {130}, producing either flattened heart-shaped or pseudohexagonal multiple contact and penetration twins (Anthony et al., 2001—2005).

Physical properties

Cleavage: distinct on {110}, imperfect on {010}, poor on {001} (Anthony et al., 2001—2005). Fracture: uneven to conchoidal (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 8.5 (Arem, 1987: 66). Density: 3.69—3.81 g/cm3 (Lazzarelli, 2012). Luminescence: weak red in SW and LW UV. Other: electrical conductivity increases with temperature.

Optical properties

Colour: various shades of green, yellow, brownish to greenish black; may be raspberry-red under incandescent light when chromian; colourless, pale shades of yellow, green, or red in transmitted light (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent, may be opaque and chatoyant with oriented inclusions (Anthony et al., 2001—2005). Lustre: vitreous (Arem, 1987: 66). Refractive index: 1.746—1.763 — anisotropic [biaxial (+)] (Lazzarelli, 2012). Birefringence: 0.007—0.013. Dispersion: low — 0.015 (Arem, 1987: 67). Pleochroism: alexandrite: X = red; Y = yellow-orange; Z = emerald-green.

Material from ‘Repository’

9 specimens: 0011 — 1.77 ct, Tanzania; 0126 — 0.85 ct, Madagascar; 0607 — 1.77 ct, Tanzania; 0667 — 0.21 ct, Madagascar; 0509 — 0.35 ct, Madagascar; 0514 — 0.24 ct, Madagascar; 0166 — 0.33 ct, Sri Lanka; 0288 — 0.50 ct, Brazil, Minas Gerais, Antônio Dias, Hematita; 0455 — 0.18 ct, Sri Lanka.

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