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).
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).
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.
