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Class: Elements

Primarily formed in pipes, less commonly in dikes, of deep-seated, igneous origin, composed of kimberlite or lamproite, and in alluvial deposits formed by their weathering. In carbonaceous achondrite and iron meteorites; may be formed by impact (Anthony et al., 2001—2005). Famous diamonds: Golden Jubilee, 545.67 carats, the largest polished gem, cut by Gabriel Tolkowsky, now part of the crown jewels of Thailand, resides in Bangkok; Cullinan I, also known as the Great Star of Africa, it weights 530.2 carats and is mounted in the Sceptre with Cross, part of the Crown Jewels of the United Kingdom; Koh-i-Noor, currently 105.60 carats, resides with the rest of the crown jewels, too; the Black Orlov Diamond, also known as the Eye of Brahma Diamond, 67.50 carats.
Diamond — specimen 0315
Diamond — specimen 0315, photo © NMNHS

Original description: unknown [prehistoric].

Type locality: unknown [prehistoric].

Type material: Muséum national d’Histoire naturelle, Paris, France, Haüy 6599 (Anthony et al., 2001—2005).

Etymology: from the Ancient Greek word αδάμας (adamas), meaning invincible, untamed, hard substance.

Distribution: numerous localities world-wide. Angola: important current alluvial production from Lunda Norte Province; Australia: Kimberley, Argyle pipe; Botswana: Jwaneng and Orapa pipes; Brazil: Minas Gerais, the area around Diamantina; Canada: Northwest Territories, Lac de Gras region, Ekati and Diavik mines; China: Liaoning Province, from pipes at the Wafangdian and Binhai mine, Shandong Province, at Changma, near Mengyin; Congo: Kasai Province, Bakwanga and Tchikapa; India: Golconda region, and near Nágpur and Bundelkhand; Russia: Sakha, from the Mir, Udatchnaya, Zarnitsa, Aikhal, and Jubileynaya pipes; Sierra Leone; South Africa: Orange, Vaal rivers and along the coast north into Namibia, in several pipes around Kimberley, at the Finsch mine, near Postmasburg (Cape Province), from the Premier mine, near Pretoria, and the Venetia mine (Transvaal) (Anthony et al., 2001—2005).



Essential elements: carbon (C).

Crystal data

Crystallography: isometric — hexoctahedral. Crystal habit: most commonly octahedral, crystals to 10 cm or more, also dodecahedral, tetrahedral, and cubic. Twinning: contact twins with {111} as twin plane; typically flattened on {111}; as penetration twins, may be repeated (Anthony et al., 2001—2005).

Physical properties

Cleavage: perfect {111} (Anthony et al., 2001—2005). Fracture: conchoidal (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 10 (Arem, 1987: 79). Density: 3.5—3.53 g/cm3 (Lazzarelli, 2012). Luminescence: occasionally fluorescent and phosphorescent. Other: has the highest thermal conductivity of any known substance (Anthony et al., 2001—2005).

Optical properties

Colour: colourless, pale yellow to deep yellow, brown, white, blue-white; less commonly in oranges, pinks, greens, blues, reds, grey to black (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: adamantine to greasy (Anthony et al., 2001—2005). Refractive index: 2.417—2.419 — isotropic (Lazzarelli, 2012). Dispersion: strong; 0.044 (Arem, 1987: 79). Pleochroism: none.

Material from ‘Repository’

3 specimens: 0314 — 0.03 ct, no precise locality [Africa]; 0315 — 0.03 ct, no precise locality [Africa]; 0599 — 0.04 ct, no precise locality [Africa].

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