sodalite

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sodalite An important group of silicate minerals belonging to the feldspathoids and including sodalite Na8[Al6Si6O24]Cl2, nosean, haüyne, cancrinite, lazurite, and scapolite; sp.gr.2.27–2.88; hardness 5.5–6.0; greyish to bluish, yellow; occurs as rhombohedra or massive; vitreous lustre; occurs in nepheline syenites in association with nepheline and fluorite, and in metasomatized (see METASOMATISM) calcareous rocks near alkaline igneous intrusions.