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Class: Sulphates

Varieties | Names:

A major component in sedimentary deposits and in the cap rocks above salt domes, commonly formed by dehydration of gypsum; in igneous rocks; also an alteration product in hydrothermal mineral deposits (Anthony et al., 2001—2005).
Angelite — specimen 0736
Angelite — specimen 0736, photo © NMNHS

Original description: ‘Anhydrit’ Ludwig, C. F. , 1804. A. G. Werners Mineral — System vom Jahre 1803. Erste Klasse Erdige Fossilien. VI. Kalk — Geschlecht. In: Handbuch der Mineralogie nach A. G. Werner, Siegfried Lebrecht Crusius, Leipzig, 2: 212 [view in ‘Library’].

Type locality: Salzbergwerk, Hall Valley, Innsbruck, Inn Valley, Tyrol, Austria.

Type material: Technische Universität Bergakademie, Freiberg, Germany, 16538 (Anthony et al., 2001—2005).

Etymology: from the Greek for without water.

Distribution: numerous localities: Austria; Canada; Germany; India; Italy; Mexico; Peru; Philippines; Switzerland; USA (Anthony et al., 2001—2005).



Essential elements: oxygen (O), sulphur (S), calcium (Ca).

Crystal data

Crystallography: orthorhombic — dipyramidal. Crystal habit: crystals tabular on {010}, {100}, or {001} or equant with large pinacoidal faces; elongated along [100] or [001]; to 15 cm; typically granular, nodular, parallel or divergent fibrous, massive (Anthony et al., 2001—2005). Twinning: simple or repeatedly on {011}, common; contact twins rare on {120} (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {010}, perfect; on {100} nearly perfect; on {001} good to imperfect, yielding pseudocubic fragments (Anthony et al., 2001—2005). Fracture: uneven to splintery (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 3—3.5 (Anthony et al., 2001—2005). Density: 2.98 g/cm3 (Anthony et al., 2001—2005). Luminescence: none.

Optical properties

Colour: colourless to pale blue or violet if transparent; white, mauve, rose, pale brown or grey from included impurities; colourless in transmitted light (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: pearly on {010}, vitreous to greasy on {001}; vitreous on {100} (Anthony et al., 2001—2005). Refractive index: 1.567—1.618 — anisotropic [biaxial (+)] (Anthony et al., 2001—2005). Dispersion: strong (Anthony et al., 2001—2005). Pleochroism: for violet varieties: X = colourless to pale yellow or rose; Y = pale violet or rose; Z = violet (Anthony et al., 2001—2005).

Material from ‘Repository’

2 specimens: 0736 — 2.32 ct, Peru; 0737 — 3.18 ct, Peru.

Gallery view