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- Title
Crystal structure of manganese-rich variety of eudialyte from Suchina Hill, India, and manganese ordering in eudialyte-group minerals.
- Authors
Aksenov, S.; Rastsvetaeva, R.; Mitchell, R.; Chakrabarty, A.
- Abstract
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. R3 m, 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)(Ca,Mn)Mn(Si,Nb)Zr[SiO](OH,Cl,HO). It is established that Mn atoms occupy three sites: two subsites in five-vertex polyhedra M2 a and M2 b, 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.
- Subjects
INDIA; CRYSTAL structure; MANGANESE isotopes; HYDROTHERMAL deposits; ALBITE; X-ray diffraction; EUDIALYTE; GEOCHEMISTRY
- Publication
Crystallography Reports, 2014, Vol 59, Issue 2, p146
- ISSN
1063-7745
- Publication type
Article
- DOI
10.1134/S1063774514020023