Crystal structure of hydrogen-bearing vuonnemite from the Lovozero alkaline massif

Hydrogen-bearing vuonnemite from the Shkatulka hyperagpaitic pegmatite (the Lovozero alkaline massif, Kola Peninsula) was studied by single-crystal X-ray diffraction. The triclinic unit-cell parameters are as follows: a = 5.4712(1) Å, b = 7.1626(1) Å, c = 14.3702(3) Å, α = 92.623(2)°, β = 95.135(1)°, γ = 90.440(1)°, sp. gr. P1, R = 3.4%. The Na+ cations and H2O molecules are ordered in sites between the packets. The water molecules are hydrogen bonded to the PO4 tetrahedra.