Haüyne

Class: Silicates
Group: Sodalite

Varieties | Names:

In phonolites and related leucite- or nepheline-rich igneous rocks; less commonly in nepheline-free extrusives (Anthony et al., 2001—2005).

Lapis lazuli — specimen 0604, photo © NMNHS

Original description: Bruun-Neergard, T. C., 1807. De la haüyne, nouvelle substance minérale — Journal des Mines 21: 365 [view in ‘Library’].

Type locality: ‘les environs du lac de Nemi’ [Lake Nemi], Alban Hills, Lazio, Italy (Bruun-Neergard, 1807: 365).

Type material: unknown.

Etymology: named after Abbé René Just Haüy, French mineralogist, father of the modern crystallography.

Distribution: China; Germany: Eifel district; Italy: Lazio; USA, and others (Anthony et al., 2001—2005).

Chemistry

(Na,Ca)4-8(Al6Si6O24)(SO4,S,Cl)1-2

Essential elements: oxygen (O), sodium (Na), aluminium (Al), silicon (Si), sulphur (S), chlorine (Cl), calcium (Ca).

Crystal data

Crystallography: isometric — hextetrahedral. Crystal habit: crystals dodecahedra or pseudo-octahedra, to 3 cm; in rounded grains. Twinning: on {111}, common, rarely as penetration twins; also as polysynthetic or contact twins (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {110}, distinct (Anthony et al., 2001—2005). Fracture: conchoidal to uneven (Arem, 1987: 109). Tenacity: brittle (Arem, 1987: 109). Hardness: 5.5—6 (Arem, 1987: 109). Density: 2.44—2.5 g/cm3 (Anthony et al., 2001—2005). Luminescence: usually none; sometimes orange-red in LW (Arem, 1987: 110).

Optical properties

Colour: bright blue to greenish blue; white or shades of black, grey, brown, green, yellow, red; colourless or pale blue in thin section (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous to greasy (Arem, 1987: 109). Refractive index: 1.494—1.509 — isotropic (Anthony et al., 2001—2005). Dispersion: none. Pleochroism: none.

Material from ‘Repository’

1 specimen: 0604 — 2.53 ct, Afghanistan.

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