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Rastsvetaeva R. K. Chukanov N. V. Pekov I. V. Varlamov D. A. Kazheva O. N. 《Crystallography Reports》2022,67(2):166-171
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been... 相似文献
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Rastsvetaeva R. K. Chukanov N. V. Möckel S. Dudka A. P. Aksenov S. M. 《Crystallography Reports》2020,65(1):27-32
Crystallography Reports - The crystal structure of a high-symmetry representative of the eudialyte group from the Norra Kärr massif (Sweden) has been investigated by X-ray diffraction analysis... 相似文献
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R. K. Rastsvetaeva N. V. Chukanov V. A. Zaitsev S. M. Aksenov K. A. Viktorova 《Crystallography Reports》2018,63(3):349-357
An eudialyte group mineral, found in pegmatites of the Odikhincha massif (the northern part of the Siberian platform), has been investigated using X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The mineral is characterized by a high strontium content and a low chlorine content. It has a trigonal unit cell with the following parameters: a = 14.2700(6) Å and c = 30.057(1) Å; V = 5300.6(1) Å3; sp. gr. R3m. The structure has been refined to R = 0.047 in the anisotropic approximation of atomic displacements using 1697F > 4σ(F). The idealized formula (Z = 3) was found to be Na12Sr2Ca6Fe 3 2+ Zr3NbSi25O72(OH,O)4Cl(Н2О)0.2. The chemical composition and structure of this mineral are close to those of taseqite; however, it differs from the holotype sample by a low chlorine content and peculiarities of cation distribution over basic structure sites. A comparative analysis of strontium-rich eudialytes has revealed their important crystallochemical feature: selective concentration of strontium in the N4 site. Thus, taseqite, along with heterophyllosilicates, may play a role of strontium concentrator in agpaitic pegmatites. 相似文献
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Crystallography Reports - The first representative of the eudialyte group with a primitive unit cell has been investigated by X-ray diffraction analysis, electron probe microanalysis, and IR... 相似文献
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The crystal structure of a new representative of the eudialyte family was studied. This mineral is characterized by a low calcium content and by ordering the elements that isomorphically replace calcium, which lowers the symmetry from R3m to R3. The structure of the sample under study consists of the six-membered rings with two octahedra of substantially different volumes, one occupied mainly by manganese and the other, mainly by sodium and characterized by the average distances of 2.22 and 2.45 Å, respectively. The formation of such octahedra is the most characteristic structural feature of the third low-symmetry mineral of the eudialyte family. 相似文献
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The structure of a new sodium-rich representative of the eudialyte group with the ideal formula (Na,Sr, K)35Ca12Fe3Zr6TiSi51O144(O,OH,H2O)9Cl3 was established by the X-ray diffraction analysis (R = 0.054 based on 3503 |F|). The unit-cell parameters are a = 14.239(1), c = 60.733(7) Å, V = 10663.9 Å3, sp. gr. R3. The mineral structure is characterized by in-layer order of cations resulting in doubling of the c-parameter and the formation of two modules, the composition and the structure of one of which corresponds to eudialyte (with an impurity of kentbrooksite), the prototype of the second module is alluaivite. Lowering of the symmetry is caused by ordering of Ca atoms and the Ca-replacing elements in the alluaivite module and by the displacements of the alkali cations from the m plane. 相似文献
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S. M. Aksenov R. K. Rastsvetaeva R. H. Mitchell A. Chakrabarty 《Crystallography Reports》2014,59(2):146-154
The crystal structure of eudialyte of hydrothermal genesis from Sushina Hill, India, where it was found associated with potassium feldspathoid, albite, aegirine, and nepheline, has been solved by X-ray diffraction analysis. One specific feature of the chemical composition of this mineral is a low content of CaO (7–8.5 wt %) and an elevated manganese content (9–10.5 wt % MnO). When compared with eudialytes of magmatic genesis, this eudialyte is enriched in Nb, Sr, Y, and rare earth elements (REEs). It is described within the sp. gr. R3m, with the unit-cell parameters a = 14.2483(3) Å and b = 30.294(1) Å; R = 4.7%. The idealized formula (Z = 3) is (Na,□,Sr)15(Ca,Mn)6Mn3(Si,Nb)2Zr3[Si24O72](OH,Cl,H2O)5.5. It is established that Mn atoms occupy three sites: two subsites in five-vertex polyhedra M2a and M2b, spaced by a distance of 0.87 Å and characterized by occupancies of 0.51 and 0.49, respectively, and the M1 site in the octahedron of six-membered ring, jointly with Ca and REE. With allowance for the established features of chemical composition and structure, the mineral under study can be considered as a strontium-rich variety of kentbrooksite. 相似文献
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