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Class: Silicates
Group: Feldspar

Varieties | Names:

Common in plutonic felsic rocks, as granites, granite pegmatites, syenites; in metamorphic rocks; in hydrothermal veins (Anthony et al., 2001—2005).
Amazonite — specimen 0101
Amazonite — specimen 0101, photo © NMNHS

Original description: ‘Mikroklin’ Breithaupt, J. F. A., 1830. Ueber die Felsite und einige deue Specien ihres Geschlechts — Journal für Chemie und Physik 60: 324—327 [view in ‘Library’].

Type locality: Arendal, Aust-Agder; Stavern, Larvik, Vestfold, Norway.

Type material: unknown.

Etymology: from the Greek for little and inclined, for the small deviation of the cleavage planes from 90°.

Distribution: Australia; Brazil: Minas Gerais; Canada: at Bancroft, Ontario; Italy; Madagascar; Namibia; Norway: Arendal and Larvik; Russia: Kola Peninsula and Urals; Switzerland; USA (Anthony et al., 2001—2005).



Essential elements: oxygen (O), aluminium (Al), silicon (Si), potassium (K).

Crystal data

Crystallography: triclinic — pinacoidal. Crystal habit: prismatic crystals elongated along [001] or [100], perhaps the largest of any species, to 50 m; granular, massive. Twinning: Carlsbad, Baveno, and Manebach laws very common; polysynthetic twinning on the Albite and Pericline laws give an orthogonal grid pattern on (001) (Anthony et al., 2001—2005).

Physical properties

Cleavage: perfect on {001} and {010}; partings on {100}, {110}, {110}, and {201} (Anthony et al., 2001—2005). Fracture: uneven (Anthony et al., 2001—2005). Tenacity: brittle (Anthony et al., 2001—2005). Hardness: 6—6.5 (Arem, 1987: 93). Density: 2.55—2.63 g/cm3 (Lazzarelli, 2012). Luminescence: none. Radioactivity: GRapi 200.97.

Optical properties

Colour: white, pale cream-yellow; red, green, blue; colourless in thin section (Anthony et al., 2001—2005). Diaphaneity: transparent to translucent (Anthony et al., 2001—2005). Lustre: vitreous (Anthony et al., 2001—2005). Refractive index: 1.514—1.539 — anisotropic [biaxial (-)] (Lazzarelli, 2012). Birefringence: 0.008—0.01. Dispersion: weak (Anthony et al., 2001—2005). Pleochroism: weak.

Material from ‘Repository’

2 specimens: 0100 — 6.92 ct, Brazil; 0101 — 4.64 ct, Brazil.

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