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A new mineral majzlanite, ideally K2Na(ZnNa)Ca(SO4)4, was found in high-temperature exhalative mineral assemblages in the Yadovitaya fumarole, Second scoria cone of the Great Tolbachik Fissure Eruption (1975–1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Majzlanite is associated closely with langbeinite and K-bearing thénardite. Majzlanite is grey with a bluish tint, has a white streak and vitreous lustre. The mineral is soluble in warm water. Majzlanite is monoclinic,C2/c,a= 16.007(2),b= 9.5239(11),c= 9.1182(10) Å, β = 94.828(7)°,V= 1385.2(3) Å3andZ= 16. The eight strongest lines of the X-ray powder diffraction pattern are [d, Å (I, %)(hkl)]: 3.3721(40)($\bar{3}$12), 3.1473(56)($\bar{4}$02), 3.1062(65)($\bar{2}$22), 2.9495(50)($\bar{1}$31), 2.8736(100)($\bar{1}$13), 2.8350(70)(421), 2.8031(45)(511) and 2.6162(41)($\bar{5}$12). The following structural formula was obtained: K2Na(Zn0.88Na0.60Cu0.36Mg0.16)(Ca0.76Na0.24)(S0.98Al0.015Si0.005O4)4. The chemical composition determined by electron-microprobe analysis is (wt.%): Na2O 9.73, K2O 15.27, ZnO 11.20, CaO 7.03, CuO 4.26, MgO 1.07, Al2O30.47, SO351.34, SiO20.12, total 100.49. The empirical formula calculated on the basis of 16 O apfu is K1.99Na1.93Zn0.84Ca0.77Cu0.33Mg0.16(S3.94Al0.06Si0.01)O16and the simplified formula is K2Na(Zn,Na,Cu,Mg)Σ2(Ca,Na)(SO4)4. No natural or synthetic compounds directly chemically and/or structurally related to majzlanite are known to date. The topology of the heteropolyhedral framework in majzlanite is complex. An interesting feature of the structure of majzlanite is an edge-sharing of ZnO6octahedra with SO4tetrahedra.

The new mineral lussierite (IMA2018-101), Na10[(UO2)(SO4)4](SO4)2(H2O)3, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as pale green–yellow prisms or blades in a secondary assemblage with belakovskiite, ferrinatrite, halite, ivsite, metavoltine and thénardite. The streak is white and the fluorescence is bright cyan under 365 nm ultraviolet light. Crystals are transparent with vitreous lustre. The tenacity is brittle, the Mohs hardness is 2½, the fracture is irregular and no cleavage was observed. The mineral is easily soluble in H2O and has a measured density of 2.87(2) g cm–3. Lussierite is optically biaxial (+), with α = 1.493(1), β = 1.505(1) and γ = 1.518(1) (white light); 2Vmeas.= 88(1)°; dispersion isr>v, moderate; pleochroism:X= colourless,YandZ= green yellow (X 2σI) contains a [(UO2)(SO4)4]6–uranyl sulfate cluster in which one SO4tetrahedron shares an edge (bidentate linkage) with the UO7pentagonal bipyramid. The uranyl sulfate clusters occur in layers and are linked through a complex network of bonds involving Na+cations, isolated SO4tetrahedra and isolated H2O groups.

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.

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.

The new mineral shilovite, the first natural tetrammine copper complex, was found in a guano deposit located on the Pabellón de Pica Mountain, near Chanabaya, Iquique Province, Tarapacá Region, Chile. It is associated with halite, ammineite, atacamite (a product of ammineite alteration) and thénardite. The gabbro host rock consists of amphibole, plagioclase and minor clinochlore, and contains accessory chalcopyrite. The latter is considered the source of Cu for shilovite. The new mineral occurs as deep violet blue, imperfect, thick tabular to equant crystals up to 0.15 mm in size included in massive halite. The mineral is sectile. Its Mohs hardness is 2. Dcalc is 1.92 g cm–3. The infrared spectrum shows the presence of NH3 molecules and NO3– anions. Shilovite is optically biaxial (+), α = 1.527(2), β = 1.545(5), γ = 1.610(2). The chemical composition (electron-microprobe data, H calculated from ideal formula, wt.%) is Cu 26.04, Fe 0.31, N 30.8, O 35.95, H 4.74, total 100.69. The empirical formula is H12.56(Cu1.09Fe0.01)N5.87O6.00. The idealized formula is Cu(NH3)4(NO3)2. The crystal structure was solved and refined to R = 0.029 based upon 2705 unique reflections having F > 4σ(F). Shilovite is orthorhombic, space group Pnn2, a = 23.6585(9), b = 10.8238(4), c = 6.9054(3) Å, V = 1768.3(1) Å3, Z = 8. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are: 5.931 (41) (400), 5.841 (100) (011), 5.208 (47) (410), 4.162 (88) (411), 4.005 (62) (420), 3.462 (50) (002), 3.207 (32) (031), 2.811 (40) (412).

The sodium-magnesium hydrated double salt konyaite, Na2Mg(SO4)2·5H2O, has been studied by single-crystal X-ray diffraction and thermogravimetry on synthetic samples and by quantitative X-ray diffraction utilizing the Rietveld method on natural samples from the Mount Keith mine, Western Australia. Konyaite crystallizes in space groupP21/c, with the cell parameters:a= 5.7594(10),b= 23.914(4),c= 8.0250(13) Å, β = 95.288(9)°,V= 1100.6(3) Å3and Z = 4. The crystal structure has been refined toR1= 3.41% for 2155 reflections [Fo>4σ(Fo)] and 6.44% for all 3061 reflections, with all atoms located.Quantitative phase analysis utilizing the Rietveld method was undertaken on five samples of konyaite-bearing mine tailings from the Mount Keith Nickel Mine, Western Australia. Konyaite was found to decompose over time and after 22 months had transformed to other sulphate and amorphous phases. Blödite did not increase in any ofthe samples indicating that konyaite may not always transform to blödite. Over the same time frame, synthetic konyaite completely decomposed to a mixture of thenardite (Na2SO4), hexahydrite (MgSO4·6H2O), blödite (Na2Mg(SO4)2·4H2O) and löweite (Na12Mg7(SO4)13). Detection of konyaite and other Mg-rich sulphates is important in terms of CO2fixation. Magnesium bound to sulphate mineral phases reduces the overall potential of tailings piles to lock up atmospheric carbon in Mg carbonates, such as hydromagnesite. Amorphous sulphates are also highly reactive and may contribute to acid mine drainage ifpresent in large quantities, and may dissolve carbonate phases which have already sequestered carbon.

Tausoare Cave is renowned in Romania for its gypsum and mirabilite speleothems. Of interest are the white crystalline speleothems formed on the floor of the ‘Sala de Mese’ (Dining Room) that were previously described as consisting of mirabilite. The samples we collected reveal crystals of two different habits. One shows the characteristic mirabilite fibrous crystals (cotton-like speleothem) while the other formed bladed and short prismatic crystals which comprise the delicate ‘cave flowers’. The mineral association was characterized by means of X-ray analysis, scanning electron microscopy and electron microprobe. Beside thenardite (dehydration product of mirabilite) we also identified three sulphate minerals: leonite [K2Mg(SO4)2·4H2O], syngenite [K2Ca(SO4)2·H2O] and konyaite [Na2Mg(SO4)2·5H2O]. Of these, leonite and konyaite have never been reported in a cave environment. This paper describes the mineralogy of this particular sulphate deposit and offers some viewpoints on the crystallogenesis.

Large thenardite crystals have been sampled at New Agorgott, in the Taoudenni area of northern Mali. They are still in equilibrium with a pressurized NaCl saturated brine capped by a halite layer. Clays located about 1 m above the thenardite occurrence have been dated at 6760 y.BP. The crystals contain numerous, large, brine and solid inclusions. Microcryscopic studies show that the fluids can be explained by the addition of MgCl2 to the Na2SO4-NaCl-H2O system (eutectic temperature: −31 to −35°C; possible bloedite Na2Mg(SO4)2.4H2O formed after freezing). The homogenization temperatures of primary fluid inclusions are in the range 28 to 50°C. In order to understand the significance of the highest Th values, overheating experiments under 1 bar pressure were performed at different heating rates up to 170°C. The results are as follows:(i) When the temperature of stretching (TOh) is higher than about 10°C, overheating is recorded and fossilized (identical Th after some hours, several days or 8 months storage at 5°C).(ii) The lowest Th values (28°C) are probably near the formation temperature of thenardite; the highest ones reflect stretching under present desert conditions.(iii) With TOh lower than about 60°C, a fair correlation is observed between Th and TOh.Finally, taking into account recent natural overheating, the fluid inclusion data are compatible with the formation of thenardite from underground brines later than the beginning of desert conditions in the Taoudenni area (i.e. about 3000 y.BP).

SummaryBurkeite (Na6CO3(SO4)2) is found as a surface mineral in the north of Kenya associated with thenardite and halite and in the Konya basin in Turkey associated with trona and halite. The cell dimensions of a natural burkeite are a = 7.070, b = 9.220, c = 5.173 Å. The Gibbs energy of burkeite is estimated in relation to other sodium carbonates and sulphates. Δ (burkeite) = 3594.2 ± 3 kJ.