The new mineral saranchinaite, ideally Na2Cu(SO4)2, was found in sublimates of the Saranchinaitovaya fumarole, Naboko Scoria Cone, Tolbachik volcano, Kamchatka, Russia. Its discovery and study has enabled the characterization of the thermal decomposition of kröhnkite and provided an insight into the high-temperature behaviour of other kröhnkite-type materials. Saranchinaite is monoclinic, P21, a = 9.0109(5), b = 15.6355(8), c = 10.1507(5) Å, β = 107.079(2)°, V = 1367.06(12) Å3, Z = 8 and R1 = 0.03. Saranchinaite is a unique mineral in that two of its four independent Cu sites display a very unusual Cu2+ coordination environment with two weak Cu–O bonds of ~2.9–3.0 Å, resulting in [4+1+2] CuO7 polyhedra. Each of the Cu-centred polyhedra shares common corners with SO4 tetrahedra resulting in a [Cu4(SO4)8]8– framework with a complex channel system occupied by Na atoms. Saranchinaite is sensitive to moisture and transforms into kröhnkite within one week when exposed to open air at 87% relative humidity and 25°C. High-temperature X-ray diffraction studies were performed for both kröhnkite (from La Vendida mine, Antofagasta Region, Chile) and saranchinaite. During thermal expansion kröhnkite retains its strongly anisotropic character up to its full dehydration and the formation of saranchinaite at ~200°C, which then transforms back into kröhnkite after exposure to open air. The thermal expansion of saranchinaite is more complex than that of kröhnkite. Saranchinaite is stable up to 475°C with subsequent decomposition into tenorite CuO, thénardite Na2SO4 and unidentified phases.

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Itelmenite, ideally Na2CuMg2(SO4)4, was found in a fumarole of the Naboko scoria cone of the Tolbachik volcano Fissure Eruption (2012–2013), Kamchatka Peninsula, Russia. Itelmenite occurs as irregularly shaped grains as well as microcrystalline masses associated with anhydrite, saranchinaite, hermannjahnite, euchlorine, thénardite, aphthitalite and hematite. Itelmenite is orthorhombic, Pbca, a = 9.568(2) Å, b = 8.790(2) Å, c = 28.715(8) Å, V = 2415.0(11) Å3 and Z = 4 (from single-crystal diffraction data). The nine strongest lines of the powder X-ray diffraction pattern are [d(I)(hkl)]: 7.9614(41)(102), 7.1803(32)(004), 5.9122(64)(112), 3.8455(87)(122), 3.6292(52)(214), 3.3931(62)(215), 3.0003(44)(027), 2.9388(100)(312) and 2.4975(56)(230). The chemical composition determined by the electron-microprobe analysis is (wt.%): Na2O 10.77, K2O 0.20, MgO 11.10, CuO 15.38, ZnO 5.61, SO3 56.42, total 99.48. The empirical formula based on O = 32 apfu is (Na3.93K0.05)Σ3.98Mg3.12(Cu2.19Zn0.78)Σ2.97S7.97O32. The simplified formula is Na2CuMg2(SO4)4 taking into account structural data. The crystal structure was solved by direct methods and refined to an agreement index R1 = 0.034 on the basis of 1855 independent observed reflections. The structure of itelmenite is based on a unique type of [A2+3(SO4)4]2– (A = Mg, Cu and Zn) heteropolyhedral framework with voids filled by Na+ cations.

Single crystals of Pb 3 O 2 (SeO 3 ) have been prepared hydrothermally at 230°C. The structure (orthorhombic, Cmc2 1 , a ϭ 10.529(2), b ϭ 10.722(2), c ϭ 5.7527(12) Å , V ϭ 649.5(2) Å 3 ) has been solved by direct methods and refined to R 1 ϭ 0.059 on the basis of 615 unique observed reflections (ΗF o Η ϭ 4σ F ). The structure is based upon double [O 2 Pb 3 ] 2ϩ chains of edge-sharing [OPb 4 ] 6ϩ tetrahedra. These [O 2 Pb 3 ] 2ϩ chains run parallel to [001], and their Synthese und Kristallstruktur von Pb 3 O 2 (SeO 3 ) Inhaltsübersicht. Einkristalle von Pb 3 O 2 (SeO 3 ) wurden hydrothermal bei 230°C dargestellt. Die Struktur (orthorhombisch, Cmc2 1 ; a ϭ 10.529(2), b ϭ 10.722(2), c ϭ 5.7527(12) Å , V ϭ 649.5(2) Å 3 ) konnte durch Direkte Methoden gelöst und auf der Grundlage von 615 symmetrieunabhängigen, beobachteten Reflexen (mit ΗF o Η Ն 4σ F ) zu R 1 ϭ 0.059 verfeinert werden. Die Kristallstruktur enthält Doppelketten der Zusammensetzung [O 2 Pb 3 ] 2ϩ , die aus kantenverknüpften Ketten von [OPb 4 ] 6ϩ -Tetraedern bestehen. Diese [O 2 Pb 3 ] 2ϩ -Ketten verlaufen parallel zu [001] und sind nach Art ei-* Dr.planes are parallel to (010). The pyramidal (SeO 3 ) 2Ϫ anions are located between the chains; their triangular oxygen atom bases lie parallel to (001) and all (SeO 3 ) 2Ϫ groups are pointing in the same direction. A short compilation of [O 2 M 3 ] chains of oxocentred M 4 tetrahedra in minerals and inorganic compounds is provided. ner hexagonal-dichtesten Stabpackung parallel zur (010)-Ebene orientiert. Die pyramidalen (SeO 3 ) 2Ϫ -Anionen sind zwischen den Ketten angeordnet und halten diese zusammen. Ihre dreieckigen Sauerstoff-Grundflächen kommen parallel (001) zu liegen und sämtliche (SeO 3 ) 2Ϫ -Gruppen zeigen in die gleiche Richtung. Zum Abschluß wird eine kurze Zusammenstellung von [O 2 M 3 ]-Ketten aus sauerstoffzentrierten M 4 -Tetraedern in Mineralen und anorganische Verbindungen gegeben.

Dobrovolskyite, Na4Ca(SO4)3, is a new sulfate mineral from the Great Tolbachik fissure eruption, Kamchatka peninsula, Russia. It occurs as aggregates of tabular crystals up to 1–2 mm in maximum dimension, with abundant gas inclusions. The empirical formula calculated on the basis of O = 12 is (Na3.90K0.10)Σ4(Ca0.45Mg0.16Cu0.12Na0.10)Σ0.83S3.08O12. The crystal structure of dobrovolskyite was determined using single-crystal X-ray diffraction data as: trigonal, R3, a = 15.7223(2), c = 22.0160(5) Å, V = 4713.1(2) Å3, Z = 18 and R1 = 0.072. The Mohs’ hardness is 3.5. The mineral is uniaxial (+), with ω = 1.489(2) and ɛ = 1.491(2) (λ = 589 nm). The seven strongest lines of the powder X-ray diffraction pattern [d, Å (I, %)(hkl)] are: 11.58(40)(101); 5.79(22)(202); 4.54(18)(030); 3.86(88)(033); 3.67(32)(006); 2.855(50)(306); and 2.682(100)(330). The mineral is named in honour of Prof. Dr. Vladimir Vitalievich Dolivo-Dobrovolsky (1927–2009), one of the leading Russian scientists in the field of petrology, crystal optics and crystal chemistry. The crystal structure of dobrovolskyite can be described as composed of three symmetrically independent rods running parallel to the c axis. The rods consist of six octahedral–tetrahedral [Na(SO4)6]11– or [Ca(SO4)6]10– clusters of central octahedra sharing common corners with six adjacent SO4 tetrahedra. Alternatively, the crystal structure of the mineral can be described as a 12-layer ABACABACABAC eutactic array of Na+ and Ca2+ cations, and vacancies with disordered (SO4) tetrahedra in interstices. Dobrovolskyite and similar minerals probably formed upon cooling of a high-temperature phase with disordered cation and anion arrangements.