Abstract

Chemical and structural variations of 11 minerals of the cancrinite group having an Al,Si,O framework of the AB type are summarized and discussed. The total number of chemically studied samples is 360 (our data and literature data): cancrinite 192 and 35, vishnevite 21 and 13, cancrisilite 19 and 10, kyanoxalite and oxalate-rich intermediate members of the cancrinite– kyanoxalite series 12 and 0, davyne 10 and 23, depmeierite 2 and 0, balliranoite 1 and 0, hydroxycancrinite 0 and 1, quadridavyne 0 and 10, microsommite 0 and 8, and pitiglianoite 0 and 3. We provide original structural data for nine samples of distinct varieties of cancrinite and one sample of cancrisilite, as well as published structural data on the above-listed minerals. The major topics are the distribution and ratios of extra-framework components, cations (Na+, Ca2+, K+), anions (CO32−, SO42−, Cl, C2O42−, PO43−) and H2O, with special emphasis on oxalate and phosphate anions. The idealized formula of cancrinite has been refined: Na7Ca[Al6Si6O24](CO3)1.5•2H2O. The solid-solution series with coupled substitutions in the framework and extra-framework portions are discussed, as is the genetic aspect of crystal chemistry of cancrinite-group minerals with a AB-type framework.

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