scholarly journals Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

2021 ◽  
Vol 85 (2) ◽  
pp. 224-232
Author(s):  
Dan Holtstam ◽  
Fernando Cámara ◽  
Andreas Karlsson
Keyword(s):  
Crystal Structure ◽  
General Formula ◽  
Solid Solutions ◽  
Divalent Cations ◽  
Structure Refinement ◽  
Structure Type ◽  
Crystal Structure Refinement ◽  
Peripheral Position ◽  
Oxide Deposit ◽  
Report Data

AbstractThe margarosanite group (now officially confirmed by IMA-CNMNC) consists of triclinic Ca-(Ba, Pb) cyclosilicates with three-membered [Si3O9]6– rings (3R), with the general formula AB2Si3O9, where A = Pb, Ba and Ca and B = Ca. A closest-packed arrangement of O atoms parallel to (101) hosts Si and B cations in interstitial sites in alternating layers. The 3R layer has three independent Si sites in each ring. Divalent cations occupy three independent sites: Ca in B occupies two nonequivalent sites, Ca1 (8-fold coordinated), and Ca2 (6-fold coordinated). A (=Ca3) is occupied by Pb2+ (or Ba2+) in 6+4 coordination, or 6+1 when occupied by Ca; this third site occurs within the 3R-layer in a peripheral position. Three minerals belong to this group: margarosanite (ideally PbCa2Si3O9), walstromite (BaCa2Si3O9) and breyite (CaCa2Si3O9). So far, no solid solutions involving the Ca1 and Ca2 sites have been described. Therefore, root names depend on the composition of the Ca3 site only. Isomorphic replacement at the Ca3 sites has been noted. We here report data on a skarn sample from the Jakobsberg Mn–Fe oxide deposit, in Värmland, Sweden, representing intermediate compositions on the walstromite–margarosanite binary, in the range ca. 50–70% mol.% BaCa2Si3O9. The Pb-rich walstromite is associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite. A crystal-structure refinement (R1 = 4.8%) confirmed the structure type, and showed that the Ca3 (Ba, Pb) site is split into two positions separated by 0.39 Å, with the Ba atoms found slightly more peripheral to the 3R-layers.

The crystal structure of cesanite, Ca1+xNa4−x(SO4)3(OH)x · (1 − x)H2O, a sulphate isotypic to apatite

1983 ◽  
Vol 47 (342) ◽  
pp. 59-63 ◽  
Author(s):  
V. Tazzoli
Keyword(s):  
Crystal Structure ◽  
General Formula ◽  
Structure Refinement ◽  
Structural Features ◽  
Partial Substitution ◽  
Crystal Structure Refinement ◽  
Charge Balance ◽  
Space Group ◽  
The Relationship

AbstractCesanite, Ca1+xNa4−x(SO4)3(OH)x · (1 − x) H2O, is hexagonal, space group P63/m, a = 9.446(1) and c = 6.895(1) Å, Z = 2. The crystal structure refinement, carried out by utilizing 457 independent reflections (final R = 0.021), shows that cesanite is isotypic to hydroxyapatite. The P atom of apatite is completely replaced in cesanite by an S atom; the two independent Ca sites of apatite are occupied respectively by Na and Na + Ca, the charge balance being by partial substitution of H2O for OH− although the occupancy of the (H2O,OH−) sites is not complete. The relationship between the water vacancies and the structural features of the (Ca,Na) polyhedron is discussed. A new general formula for the apatite-wilkeite-ellestadite series is proposed.

scholarly journals Synthesis, Crystal Structure Refinement, and Electrical Conductivity of Pb(8−x)Na2Smx(VO4)6O(x/2)

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Tatiana M. Savankova ◽  
Lev G. Akselrud ◽  
Lyudmyla I. Ardanova ◽  
Alexey V. Ignatov ◽  
Eugeni I. Get’man ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Scanning Electron Microscopy ◽  
Solid Solutions ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Solid solutions of Pb(8−x)Na2Smx(VO4)6O(x/2)were studied using X-ray diffraction analysis including Rietveld refinement and scanning electron microscopy and by measuring their electrical conductivity. Crystal structure of the solid solutions was refined and the solubility region0≤x≤0.2was determined for samarium substitution for lead under the scheme2Pb2++□→2Sm3++O2-. The influence of degree of substitution on the electrical conductivity of solid solutions was established.

Green mawbyite, PbFe3+ Fe2+ 0.4Zn 0.6(AsO 4) 2OH(H 2O), from the Lagoa mine, northern Portugal

2019 ◽  
Vol 196 (2) ◽  
pp. 129-133
Author(s):  
Pedro Alves ◽  
W. Gus Mumme ◽  
Ian E. Grey ◽  
Colin M. MacRae ◽  
Robert W. Gable
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Metal Atom ◽  
Electron Microprobe ◽  
Divalent Cations ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
High Concentration ◽  
Northern Portugal ◽  
Orange Color

An occurrence of an unusual, green-coloured mawbyite was found coating arsenopyrite in a specimen from the Lagoa mine, Northern Portugal. Electron microprobe analyses combined with a single-crystal structure refinement gives the formula as PbFe3+ Fe2+ 0.4 Zn 0.6 (AsO 4) 2 O H(H2O). The change of color from the usual bright red or orange color of mawbyite is attributed to the high concentration of divalent cations, Fe2+ and Zn, in the metal atom site.

Gatedalite, Zr(Mn2+2Mn3+4)SiO12, a new mineral species of the braunite group from Långban, Sweden

2015 ◽  
Vol 79 (3) ◽  
pp. 625-634
Author(s):  
Ulf Hålenius ◽  
Ferdinando Bosi
Keyword(s):  
Crystal Structure ◽  
General Formula ◽  
Structure Refinement ◽  
Visible Spectral Range ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Oxide Deposit

AbstractGatedalite, Zr(Mn22+Mn43+)SiO12, is a new mineral of the braunite group. It is found in hausmannite-impregnated skarn together with jacobsite, Mn-bearing calcite, tephroite, Mn-bearing phlogopite, långbanite, pinakiolite and oxyplumboroméite at the Långban Mn-Fe oxide deposit, Värmland, central Sweden. The mineral occurs as very rare, small (≤60 μm), grey, submetallic, irregularly rounded anhedral grains. Gatedalite has a calculated density of 4.783 g/cm3. It is opaque and weakly anisotropic with reflectivity in air varying between 17.1 and 20.8% in the visible spectral range. Gatedalite is tetragonal, space groupI41/acd, with the unit-cell parametersa= 9.4668(6) Å,c= 18.8701(14) Å,V= 1691.1(2) Å3andZ= 8. The crystal structure was refined to anR1 index of 5.09% using 1339 unique reflections collected with MoKαX-ray radiation. The five strongest powder X-ray diffraction lines [din Å, (I), (hkl)] are: 2.730(100)(224), 2.367(12)(040), 1.6735(12)(440), 1.6707(29)(048) and 1.4267(16)(264). Electron microprobe analyses in combination with single-crystal structure refinement resulted in the empirical formula: (Zr0.494+Mn0.402+Mg0.07Ca0.02Zn0.01Ce0.013+)Σ1.00(Mn4.443+Fe0.593+Mn0.572+Mg0.41Al0.01)Σ6.02Si0.99O12. Gatedalite is a member of the braunite group (general formula AB6SiO12). It is related to braunite (Mn2+Mn63+SiO12) through the net cation exchange (Zr4++ Mn2+) → 2Mn3+, which results from the substitutions Zr4+→ Mn2+at the 8-fold coordinated site (Ain the general formula) coupled with a 2Mn2+→ 2Mn3+substitution at the 6-fold coordinated sites (Bin the general formula).

Neue Niob- und Tantalchloride der Zusammensetzung A4[M6Cl18] (A = (Ga,) In, TI; M = Nb, Ta) / New Niobium and Tantalum Chlorides of the Composition A4[M6Cl18] (A = (Ga,) In, TI; M = Nb, Ta)

1995 ◽  
Vol 50 (9) ◽  
pp. 1373-1376 ◽  
Author(s):  
Béla Baján ◽  
H.-Jürgen Meyer
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Coordination Sphere ◽  
Structure Refinement ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
Space Group ◽  
X Ray ◽  
New Compounds

AbstractThe syntheses of new compounds of the general formula A4[Nb6Cl18] (A = Ga, In, Tl) and A4[Ta6Cl18] (A = In, Tl) are reported. The indexing of their X-ray powder patterns was performed isotypically with K4Nb6Cl18]- A single-crystal structure refinement on In4[Ta6Cl18] gave the space group C2/m, Z - 2, a = 1077.7(3) pm, b = 1542.3(5) pm, c = 960.2(2) pm, β = 117.68(2) . The structure contains [Ta6Cl12Cl6]4- ions linked via I+ ions . In+ is situated in a strongly distorted coordination sphere of Cl- .

scholarly journals Barium bis[tetrafluoridobromate(III)]

IUCrData ◽  
2021 ◽  
Vol 6 (7) ◽  
Author(s):  
Sergei I. Ivlev ◽  
Florian Kraus
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Structure Type ◽  
Crystal Structure Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
Anisotropic Displacement Parameters

Single crystals of barium bis[tetrafluoridobromate(III)], Ba[BrF4]2, were obtained in the form of tiny blocks. Crystal-structure refinement of Ba[BrF4]2 from single-crystal X-ray diffraction data confirmed the previous model obtained on the basis of powder data [Ivlev et al. (2014). Eur. J. Inorg. Chem. pp. 6261–6267], but with all atoms refined with anisotropic displacement parameters. The crystal structure consists of two symmetry-independent barium cations that are each coordinated by twelve fluorine atoms, forming edge-sharing polyhedra, and an almost square-planar [BrF4]− anion. The compound crystallizes in the Ba[AuF4]2 structure type.

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