... and in the cages of the structure. The cell parameters of pitiglianoite are nearly identical to those of microsommite. However, the chemical composition of the two minerals is different, according to the coupled substitution Na + + H 2 O = Ca 2+ + Cl − between pitiglianoite and microsommite. The cell volume...

..., 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...

...–13.1 Å), while three others, namely pitiglianoite, microsommite, and quadridavyne, are characterized with their a values being multiples of this ( a = 2 a can for quadridavyne and a = a can ·3 1/2 for microsommite and pitiglianoite). Changes in a are a function of different ways in which...

...Fig. 4. Plot of (Cl-+F-) vs (SO 4 ) 2− per formula unit of “cavolinite” (this work) and davyne, microsommite and quadridavyne from the litterature ( Bariand et al. , 1968 ; Takla & Griffin, 1980 ; Hassan & Grundy, 1990 ; Bonaccorsi et al. , 1990 , 1992 , 1995, 2001 ; Bonaccorsi...

...− ,Cl − )- and CO 3 2− - end-members, respectively, and show a channel configuration analogous to that of vishnevite (for davyne) and cancrinite (for balliranoite) ( Fig. 3 ). In microsommite ( Table 1 ; Bonaccorsi et al. 2001 ), the ordered distribution along the channel of SO 4 2− groups...

... [(Na,K) 6 (SO 4 ) 0.5–1 Cl 0–1 ][Ca 2 Cl 2 ][Si 6 Al 6 O 24 ] and microsommite [(Na 4 K 2 (SO 4 )][Ca 2 Cl 2 ][Si 6 Al 6 O 24 ] has been reported ( Bonaccorsi et al. 1995 ) as well as that of pitiglianoite [(Na 4 K 2 (SO 4 )][Na 2 (H 2 O) 2 ][Si 6 Al 6 O 24 ] ( Bonaccorsi and Merlino 2005...

...Figure 4. Relationships among the unit cell of (a) davyne, (b) microsommite and (c) quadridavyne, as seen along [001]. ...

... and microsommite in calcite a few millimeters further from the end of the veinlet shown in (a). ...

... ); N  = number of layers) ( Sapozhnikov, 2004 ) of sacrofanite of ca . 5.304 Å is smaller than that of davyne, microsommite, quadridavyne, i.e . fully expanded Cl end-members of the AB cancrinite-type minerals ( Ballirano, 1994 ), as well as that of previously analysed liottite and afghanite samples...

... a few cycles of refinement, 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...

.... , 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 et al. , 1991 ) and microsommite ( Bonaccorsi et al...

...: a * = 0.5 a [sin(π/3)] −1 (for microsommite and pitiglianoite) and a ** = 0.5 a (for quadridavyne). ...

..., vishnevite, pitiglianoite, and hydroxycancrinite contain a [Na·H 2 O] + cluster, whereas in davyne, quadridavyne, and microsommite the cage contains a Ca and a Cl atom, while tiptopite contains a K atom in a cage (e.g., Hassan and Grundy 1990 ; Bonaccorsi et al. 1990 , 1994 , 2001 ; Merlino et al. 1991...

... not been accepted as a valid species by several investigators, who equated it with nepheline, microsommite, and davyne. Powder and Weissenberg X-ray diffraction data of 15 museum specimens (supplemented by single-crystal refinement of one specimen) from the only known locality of the mineral, given...