cancrinite

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cancrinite A member of the feldspathoid group of silicate minerals with a complex formula, approximately (Na,Ca,K)6–8 [AlSiO4]6(CO3,SO4,Cl)1–2.1–5H2O, it may be an alteration product of nepheline, and is related to vishnevite, the sulphate-rich variety; normally massive; occurs in nepheline syenites.