Pyrope

Class: Silicates
Group: Garnet

Varieties | Names:

In ultramafic rocks, as peridotites, kimberlites, eclogites, serpentinites. Also in amphiboles and biotite schists (Anthony et al., 2001—2005).

Pyrope — specimen 0050, photo © NMNHS

Original description: ‘Pyrop’ Ludwig, C. F., 1803. Sippschaft des granats. Pyrop — Handbuch der Mineralogie nach A. G. Werner, Siegfried Lebrécht Crusius, Leipzig: 62—67 [view in ‘Library’].

Type locality: Czech Republic.

Type material: unknown.

Etymology: from the Greek (pyropos), ‘fiery-eyed’, in allusion to the red hue.

Distribution: widespread: Brazil: Pernambuco; Czech Republic: Měrunice; Germany: Saxony, Greifendorf; Italy: Piedmont; South Africa: at the diamond mines around Kimberley; Tanzania: Umba River (Anthony et al., 2001—2005).

Chemistry

Mg3Al2(SiO4)3

Essential elements: oxygen (O), magnesium (Mg), aluminium (Al), silicon (Si).

Crystal data

Crystallography: isometric — hexoctahedral. Crystal habit: subhedral to euhedral crystals, showing the dodecahedron or trapezohedral forms, to 20 cm; also granular, massive (Anthony et al., 2001—2005).

Physical properties

Cleavage: none. Fracture: conchoidal (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 7—7.5 (Lazzarelli, 2012). Density: 3.62—3.87 g/cm3 (Lazzarelli, 2012). Luminescence: none (Arem, 1987: 104).

Optical properties

Colour: purple-red, pinkish red, red-orange, deep red to almost black; some examples are bluish green in daylight and wine-red in artificial light; colourless to pink in thin section (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous (Anthony et al., 2001—2005). Refractive index: 1.72—1.756 — isotropic (Lazzarelli, 2012). Dispersion: 0.022. Pleochroism: none.

Material from ‘Repository’

34 specimens: 0050 — 0.56 ct, Cote d’Ivoire; 0662 — 0.21 ct, Cote d’Ivoire; 0657 — 0.14 ct, USA, Arizona, Apache County, Navajo Indian Reservation; 0289 — 0.37 ct, USA, Arizona, Apache County, Navajo Indian Reservation; 0141 — 0.87 ct, Tanzania, Arusha, Namanga; 0125 — 0.50 ct, Tanzania, Arusha, Namanga; 0005 — 0.81 ct, Tanzania, Arusha, Namanga; 0621 — 0.94 ct, Tanzania, Arusha, Namanga; 0647 — 0.28 ct, no precise locality [East Africa]; 0660 — 0.26 ct, no precise locality [East Africa]; 0308 — 0.57 ct, Tanzania; 0341 — 0.34 ct, Tanzania; 0262 — 0.60 ct, no precise locality [East Africa]; 0001 — 0.92 ct, no precise locality [East Africa]; 0653 — 0.35 ct, Tanzania; 0636 — 0.28 ct, no precise locality [Africa]; 0637 — 0.37 ct, no precise locality [East Africa]; 0731 — 0.80 ct, Tanzania, Tanga, Umba Valley; 0272 — 0.51 ct, Madagascar, Toliara, Androy, Bekily; 0120 — 0.61 ct, Madagascar, Toliara, Androy, Bekily; 0048 — 1.10 ct, Tanzania; 0480 — 0.46 ct, Tanzania; 0032 — 0.92 ct, Tanzania, Tanga, Umba Valley; 0230 — 0.20 ct, Tanzania; 0231 — 0.19 ct, Tanzania; 0243 — 0.11 ct, Tanzania; 0247 — 0.12 ct, Tanzania; 0237 — 0.21 ct, Tanzania; 0398 — 0.13 ct, Tanzania; 0268 — 0.19 ct, no precise locality [East Africa]; 0269 — 0.18 ct, no precise locality [East Africa]; 0238 — 0.14 ct, Tanzania; 0239 — 0.12 ct, Tanzania; 0399 — 0.20 ct, Tanzania.

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