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Class: Silicates

In boron-rich igneous and sedimentary rocks; in metamorphosed anorthosite complexes (Anthony et al., 2001—2005).

Original description: Lorenzen, J., 1884. Undersøgelse af Mineralier fra Grønland — Meddelelser om Grønland 7: 1—32 [view in ‘Library’].

Type locality: Fiskenaes old harbour, Fiskenaes, Nuuk, Sermersooq, Greenland.

Type material: Københavns Universitet, Copenhagen, Denmark, 1883.754 (Anthony et al., 2001—2005).

Etymology: in honour of Andreas Nikolaus Kornerup, Danish geologist.

Distribution: Germany: Waldheim, Saxony; Greenland; Madagascar; Norway; South Africa; Sri Lanka: gem gravels of the Ratnapura; Tanzania (Anthony et al., 2001—2005).



Essential elements: hydrogen (H), boron (B), oxygen (O), magnesium (Mg), aluminium (Al), silicon (Si).

Crystal data

Crystallography: orthorhombic — dipyramidal. Crystal habit: crystals prismatic, to over 20 cm, rarely terminated; as radiating aggregates (Anthony et al., 2001—2005).

Physical properties

Cleavage: good on {110} (Anthony et al., 2001—2005). Fracture: conchoidal (Arem, 1987: 120). Tenacity: brittle (Arem, 1987: 120). Hardness: 6.5 (Lazzarelli, 2012). Density: 3.25—3.45 g/cm3 (Lazzarelli, 2012). Luminescence: none.

Optical properties

Colour: colourless, white, blue, green, dark green, greenish yellow, yellow-brown, black (Anthony et al., 2001—2005). Diaphaneity: transparent to opaque (Anthony et al., 2001—2005). Lustre: vitreous (Arem, 1987: 120). Refractive index: 1.660—1.685 — anisotropic [biaxial (-)] (Lazzarelli, 2012). Birefringence: 0.012—0.017. Dispersion: 0.018 (Arem, 1987: 120). Pleochroism: X = colourless to green; Y = colourless, pale brownish yellow, pale yellowish green; Z = pale brownish green, green, light amber (Anthony et al., 2001—2005).

Material from ‘Repository’

5 specimens: 0427 — 0.59 ct, Sri Lanka, North Central Province, Elahara; 0104 — 1.35 ct, Sri Lanka; 0436 — 0.66 ct, Sri Lanka; 0453 — 0.22 ct, Madagascar; 0644 — 0.44 ct, Sri Lanka.

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