Abstract
A new cancrinite-group mineral with composition (Na,Ca)24K10[(Si,Al)60O120](SO4)5.6Cl1.5(CO3)0.4·11H2O from the Sacrofano Caldera (Italy) was studied by X-ray diffraction. The unit-cell parameters are a = 12.847 A, c = 26.461 A, sp. gr. P3; the R factor is 5.7% based on 3111 reflections with F > 5σ(F). The mineral has a ten-layer stacking sequence of six-membered rings ACACBCBCBCAC…, whereas franzinite (Na,K)30Ca10[Si30Al30O120](SO4)10·2H2O having the same unit cell (sp. gr. P321) is characterized by a stacking sequence ABCABACABCAB. Both minerals contain three types of cages, including the cancrinite cage. The distinguishing feature of the analog of franzinite is that it contains the largest cages (liottite and giuseppettite) instead of the sodalite and bystrite (losod) cages found in the franzinite structure.
Published Version
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