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Class: Silicates
Group: Gadolinite-datolite

In granite and alkalic granite pegmatites (Anthony et al., 2001—2005). Faceted specimens are extremely rare.

Original description: ‘Gadolinit’ Klaproth, M. H., 1802. Chemische Untersuchung des Gadolinits — Beiträge zur Chemischen Kenntniss der Mineralkörper 3: 52—79 [view in ‘Library’].

Type locality: Ytterby, Vaxholm, Stockholm, Sweden.

Type material: unknown.

Etymology: in honour of Johan Gadolin, Finnish chemist, discoverer of yttrium.

Distribution: Austria: near Bad Gastein, Salzburg; Canada: Ontario; Norway; Sweden: Vaxholm, Ytterby; Switzerland: Ticino (Anthony et al., 2001—2005).



Essential elements: beryllium (Be), oxygen (O), silicon (Si), iron (Fe), yttrium (Y).

Crystal data

Crystallography: monoclinic — prismatic. Crystal habit: crystals rough; typically prismatic, terminated by {001}, {111}, {221}, and many other forms, to 25 cm; commonly massive (Anthony et al., 2001—2005).

Physical properties

Cleavage: none (Arem, 1987: 101). Fracture: conchoidal or splintery (Anthony et al., 2001—2005). Tenacity: brittle (Arem, 1987: 101). Hardness: 6.5—7 (Arem, 1987: 101). Density: 4.36—4.77 g/cm3 (Anthony et al., 2001—2005). Luminescence: none.

Optical properties

Colour: black, greenish black, brown; grass-green to olive-green in thin fragments (Anthony et al., 2001—2005). Diaphaneity: opaque, nearly transparent in thin fragments (Anthony et al., 2001—2005). Lustre: vitreous to greasy (Arem, 1987: 101). Refractive index: 1.77—1.82 — anisotropic [biaxial (+)] (Arem, 1987: 101). Birefringence: 0.05. Dispersion: distinct (Anthony et al., 2001—2005). Pleochroism: none.

Material from ‘Repository’

1 specimen: 0087 — 2.21 ct, Norway.

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