Belomarinaite, ideally KNaSO4, is a new sulfate mineral discovered in the Toludskoe lava field, formed during the 2012–2013 Tolbachik Fissure eruption. The mineral occurs as arborescent aggregates of tabular crystals (1 mm × 0.3 mm × 0.1 mm) comprising hematite impurities. The average size of the aggregates is 0.5–0.7 mm. The empirical formula is (K0.95Na0.92Cu0.04)Σ1.91S1.01O4. The crystal structure of belomarinaite was determined using single-crystal X-ray diffraction data; the space group is P3m1, a = 5.6072(3), c = 7.1781(4) Å, V = 195.45(2) Å3, Z = 2 and R1 = 2.6%. In the crystal structure of belomarinaite, there are six cation sites: the [4]S1 and [4]S2 sites are occupied by S, the [6]Na and [12]K sites are occupied by Na and K, respectively, giving Na0.5K0.5 apfu and the [10]M1 and [10]M2 sites are occupied by Na0.78K0.22 and K0.78Na0.22 apfu, respectively. The crystal structure is a framework of SO4 tetrahedra, Na octahedra and K, M1 and M2 polyhedra. Belomarinaite is isostructural with the synthetic compound KNaSO4. In belomarinaite, Na and K are disordered over M1 and M2 sites; in its synthetic analogue, Na and K are ordered over M1 and M2 sites, respectively. The Mohs’ hardness is 2–3. The mineral is uniaxial (+), with ω = 1.485(3) and ε = 1.488(3) (λ = 589 nm). The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 4.022(31)(101); 3.591(26)(002); 2.884(74)(102); 2.800(100)(110); 2.391(16)(003); 2.296(8)201; 2.008(38)(022); and 1.634(10)(212). The mineral was named in honour of Russian volcanologist Marina Gennadievna Belousova (b. 1960) for her significant contributions to the monitoring of the Tolbachik Fissure eruption.

You do not currently have access to this article.