Ivsite, Na3H(SO4)2, a new mineral from volcanic exhalations of fumaroles of the Fissure Tolbachik Eruption of the 50th Anniversary of the Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences

Fine-granular (<0.1 mm) flattened colorless transparent crystals of ivsite form white aggregates. The empirical formula (Na 2.793 Cu 0.056 ) 2.849 HS 2.016 O 8 is close to the ideal Na 3 H(SO 4 ) 2 . The structure was refined up to R = 0.040. Ivsite has a monoclinic symmetry, P 2 1 / c , a = 8.655(1) Å, b = 9.652(1) Å, c = 9.147(1) Å, β = 108.76(1)°, V = 723.61(1) Å 3 , Z = 4. Na atoms occur at six- and seven-fold sites (NaO 6 and NaO 7 ); S atoms, in isolated SO 4 tetrahedrons; these polyhedrons form a three-dimensional framework. The diagnostic lines of powder diffraction patterns ( d [Å]– I – hkl ) are 4.010–53–12-1, 3.949–87–012, 3.768–100–210, 3.610–21–20-2, 3.022–22–031, 2.891–42–22-2, 2.764–49–31-1, and 2.732–70–13-1.