17 research outputs found
Kamenevite, K2TiSi3O9·H2O, a new mineral with microporous titanosilicate framework from the Khibiny alkaline complex, Kola peninsula, Russia
Dravertite, CuMg(SO4)2, a new mineral species from the Tolbachik volcano, Kamchatka, Russia
New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. IX. Arsenatrotitanite, NaTiO(AsO4)
Third-generation synchrotron x-ray diffraction of 6-ÎŒm crystal of raite, âNa(3)Mn(3)Ti(0.25)Si(8)O(20)(OH)(2)â 10H(2)O, opens up new chemistry and physics of low-temperatureâminerals
The crystal structure of raite was solved and refined from data collected at Beamline Insertion Device 13 at the European Synchrotron Radiation Facility, using a 3 Ă 3 Ă 65 ÎŒm single crystal. The refined lattice constants of the monoclinic unit cell are a = 15.1(1) â«; b = 17.6(1) â«; c = 5.290(4) â«; ÎČ = 100.5(2)°; space group C2/m. The structure, including all reflections, refined to a final R = 0.07. Raite occurs in hyperalkaline rocks from the Kola peninsula, Russia. The structure consists of alternating layers of a hexagonal chicken-wire pattern of 6-membered SiO(4) rings. Tetrahedral apices of a chain of Si six-rings, parallel to the c-axis, alternate in pointing up and down. Two six-ring Si layers are connected by edge-sharing octahedral bands of Na(+) and Mn(3+) also parallel to c. The band consists of the alternation of finite MnâMn and NaâMnâNa chains. As a consequence of the misfit between octahedral and tetrahedral elements, regions of the SiâO layers are arched and form one-dimensional channels bounded by 12 Si tetrahedra and 2 Na octahedra. The channels along the short c-axis in raite are filled by isolated Na(OH,H(2)O)(6) octahedra. The distorted octahedrally coordinated Ti(4+) also resides in the channel and provides the weak linkage of these isolated Na octahedra and the mixed octahedral tetrahedral framework. Raite is structurally related to intersilite, palygorskite, sepiolite, and amphibole
Oyelite: new mineralogical data, crystal structure model and refined formula Ca5BSi4O13(OH)3·4H2O
A New Mineral Hanauerite, AgHgSI, and Common Crystal Chemical Features of Natural Mercury Sulphohalides
A new mineral, hanauerite, ideally AgHgSI, was found in the oxidation zone of Ag- and Hg-bearing ores at two old, abandoned mines in Rhineland-Palatinate, Germany. In a holotype specimen originating from the Schöne Aussicht Mine, Dernbach, Westerwald, it is associated with plumbogummiteâhinsdalite series of minerals and goethite. In cotype from the Friedrichssegen Mine, Bad Ems, it is associated with perroudite, goethite, and quartz. At both localities, hanauerite occurs as a prismatic crystal up to 0.15 mm long and up to 0.02 mm thick. The mineral is yellow, transparent, with an adamantine lustre. It is brittle, and cleavage was not observed. The calculated density values are 6.671 and 6.575 g cmâ3 for holotype and cotype, respectively. The empirical formulae calculated (from electron microprobe data) based on the sum of all atoms = 4 apfu are Ag0.95Hg1.00S1.01(I0.83Br0.19Cl0.03)ÎŁ1.05 for holotype and Ag0.97Hg0.97S1.05(I0.76Br0.25)ÎŁ1.01 for cotype. Hanauerite is orthorhombic, space group Pmma; the unit cell parameters (from single-crystal X-ray diffraction data; holotype/cotype) are: a = 9.932(2)/9.9256(8), b = 4.6219(19)/4.6209(2), c = 9.891(4)/9.9006(4) Ă
, V = 454.0(3)/454.19(5) Ă
3, and Z = 4. The crystal structure was studied on single crystals extracted from both holotype and cotype specimens; R1 = 0.0416 (holotype) and =0.0544 (cotype). In hanauerite, Hg2+ cations centre strongly distorted octahedra with two short HgâS bonds (Hg and S atoms build âcrankshaft-typeâ chains) and four strongly elongated HgâI bonds. The Hg-centred octahedra are connected via common edges and faces to form corrugated layers; Ag+ cations are located between these layers. Hanauerite is named in honour of the German mineral collector Dr. Alfred Hanauer (1912â1988). The common crystal chemical features of mercury sulphohalide minerals are discussed