...-FTIR spectroscopy on a sample of pitiglianoite from Monte Cavalluccio ( Bonaccorsi & Orlandi, 1996 ). A sharp and prominent band is observed in the medium-infrared range at 2351 cm -1 , which can be assigned to carbon dioxide molecules in the studied sample. Polarized-light FTIR spectra collected...

...Stefano Merlino; Marcello Mellini; Elena Bonaccorsi; Marco Pasero; Leonardo Leoni; Paolo Orlandi Abstract Pitiglianoite, ideally Na 6 K 2 Si 6 Al 6 O 24 (SO 4 )·2H 2 O, is a new aluminosilicate that occurs in ejected blocks near Pitigliano, southern Tuscany, Italy. It is hexagonal, space group P 6...

... crystal chemical and structural features and their thermal behaviour. Only K-rich pitiglianoite shows a significant negative expansion that has been attributed to the occurrence, as in the case of the zeolite erionite, of a sort of “internal cation exchange” process involving the substitution by K of H 2...

..., 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...

...-framework components. We provide IR spectra for typical samples of cancrinite, cancrisilite, kyanoxalite, hydroxycancrinite, depmeierite, vishnevite, pitiglianoite, balliranoite, davyne and quadridavyne, as well as the most unusual varieties of cancrinite-subgroup minerals (Ca-deficient cancrinite, H 2 O...

... of the SO 4 tetrahedra within the cage. The two “cancrinite” cages share a common base and contain a segment of the …Na–H 2 O…Na–H 2 O…. chain, which is a characteristic feature of the cancrinite, vishnevite, and pitiglianoite structures. The “sodalite” cages host one sulfate group that is always disordered...

... 2− for CO 3 2− groups along the cancrinite-vishnevite series is correlated with the entry of significant amounts of K in the channels; when the (Na,Ca): K is nearly = 1, there is the possibility of long-range ordering of sulfate groups and extra-framework cations, such as in pitiglianoite, which...

... a , b hydroxycancrinite [Na 6 (OH) 2 ][Na 2 (H 2 O) 2 ][Si 6 Al 6 O 24 ] 1 12.740, 5.182 P 3 a cancrisilite Na 7 Al 5 Si 7 O 24 (CO 3 )·3H 2 O 1 12.575, 5.105 P 6 3 mc a pitiglianoite [(Na 4 K 2 )(SO 4 )][Na 2 (H 2 O) 2 ][Si 6 Al 6 O 24 ] 3 22.121, 5.221 P 6 3...

... belonging to the cancrinite group lead to a better knowledge of their crystal chemistry. In particular, the structural refinements of davyne ( Hassan & Grundy, 1990 ; Bonaccorsi et al. , 1990 ), pitiglianoite ( Merlino et al. , 1991 ), and microsommite ( Bonaccorsi et al. , 2001 ), as well...

... is controlled by geometrical constraints ( Ballirano et al. , 1996b ). In addition, ordering of extra-framework Na and K cations, coupled with ordering of SO 4 anion groups, may also produce to a threefold supercell, with a pit = √3 a can of cancrinite, as indeed is the case for pitiglianoite ( Merlino...

..., difference Fourier maps clearly indicated that the M1 site was split as commonly found in other cancrinite-like minerals (davyne: Hassan & Grundy, 1990 ; Bonaccorsi et al. , 1990 , 1992 and 1995 ; microsommite: Bonaccorsi et al. , 2001 ; pitiglianoite: Merlino et al. , 1991 ; quadridavyne...