Variscite

Class: Phosphates, arsenates, vanadates
Group: Variscite

Typically deposited from phosphate-bearing waters in contact with aluminous rocks (Anthony et al., 2001—2005).

Variscite — specimen 0651, photo © NMNHS

Original description: ‘Variscit’ Breithaupt, J. F. A., 1837. Bestimmung neuer Mineralien. 4. Variscit — Journal für Praktische Chemie 10: 506—508 [view in ‘Library’].

Type locality: Meßbach quarry, Plauen, Vogtland, Saxony, Germany.

Type material: unknown.

Etymology: from the old name for Vogtland, the district in Germany which was the original source for the mineral.

Distribution: many localities: Australia; Austria; Brazil; Czech Republic; England; Germany: Meßbach; Japan; Kazakhstan; South Africa; Spain; USA: Utah (Anthony et al., 2001—2005).

Chemistry

AlPO4·2H2O

Essential elements: hydrogen (H), oxygen (O), aluminium (Al), phosphorus (P).

Crystal data

Crystallography: orthorhombic — dipyramidal. Crystal habit: uncommon in crystals; commonly fine-grained massive, nodular forms. Twinning: on {201}, rare (Anthony et al., 2001—2005).

Physical properties

Cleavage: good on {010}, poor on {001} (Anthony et al., 2001—2005). Fracture: uneven, splintery, subconchoidal to conchoidal when fine-grained or glassy (Anthony et al., 2001—2005). Tenacity: brittle (Arem, 1987: 197). Hardness: 3.5—4.5 (Arem, 1987: 197). Density: 2.2—2.61 g/cm3 (Anthony et al., 2001—2005). Luminescence: none.

Optical properties

Colour: pale to emerald-green, bluish green, colourless to white, pale shades of brown or yellow, rarely red; colourless to pale green in transmitted light (Anthony et al., 2001—2005). Diaphaneity: transparent, translucent (Anthony et al., 2001—2005). Lustre: vitreous, waxy (Anthony et al., 2001—2005). Refractive index: 1.563—1.594 — anisotropic [biaxial (-)] (Arem, 1987: 197). Birefringence: 0.031. Dispersion: no data. Pleochroism: none.

Material from ‘Repository’

3 specimens: 0076 — 4.75 ct, USA, Utah, Lucin; 0077 — 4.67 ct, USA, Utah, Lucin; 0651 — 0.65 ct, USA, Utah, Lucin.

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