Class: Silicates
Group: Sodalite
Original description: Thomson, T., 1811. A Chemical Analysis of Sodalite, a new Mineral from Greenland — Journal of Natural Philosophy, Chemistry and the Arts 29: 285—292 [
view in ‘Library’].
Type locality: Ilimaussaq, Narsaq, Kitaa, Greenland.
Type material: unknown.
Etymology: the name reflects its sodium content.
Distribution: Bolivia: Cochabamba; Canada; Germany: Eifel district; Italy: at Vesuvius, Monte Somma, Campania; Norway; Russia: Kola Peninsula (
Anthony et al., 2001—2005).
Chemistry
Na8Al6Si6O24Cl2
Essential elements: oxygen (O), sodium (Na), aluminium (Al), silicon (Si), chlorine (Cl).
Crystal data
Crystallography: isometric — hextetrahedral.
Crystal habit: crystals rare, typically dodecahedra, to 10 cm; as embedded grains or massive.
Twinning: on {111}, common, forming pseudohexagonal prisms by elongation along [111] (
Anthony et al., 2001—2005).
Optical properties
Colour: colourless, white, yellowish, greenish, light to dark blue, reddish; in thin section, colourless to grеy (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent (
Anthony et al., 2001—2005).
Lustre: vitreous to greasy (
Arem, 1987: 174).
Refractive index: 1.478—1.488 — isotropic (
Lazzarelli, 2012).
Dispersion: 0.018.
Pleochroism: none.
Material from ‘Repository’