Pitiglianoite, ideally Na6K2Si6Al6O24(SO4).2H2 O, is a new aluminosilicate that occurs in ejected blocks near Pitigliano, southern Tuscany, Italy. It is hexagonal, space group P63, with a = 22.121(3), c = 5.221(1) Å, and Z = 3. Pitiglianoite is colorless with a vitreous luster; Dmeas = 2.37(4), Dcalc= 2.394 g/cm3. Optically it is uniaxial negative with ω = 1.508(1) and ε = 1.506(1). Its crystal structure has been refined to R = 0.065 using 2799 reflections obtained with MoKα radiation on a four-circle automatic diffractometer. Pitiglianoite belongs to the cancrinite and vishnevite group of minerals, with a three-dimensional framework of alternating [SiO4] and [AlO4] tetrahedra with alkali cations, H2O molecules, and sulphate groups in the channels and in the cages of the structure.
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