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The crystal structures of the mixed-valence tellurium oxysalts tlapallite, (Ca,Pb)3CaCu6[Te34+Te6+O12]2(Te4++O3)2(SO4)2·3H2O, and carlfriesite, CaTe24+Te6+O8
Citation
Missen, OP and Kampf, AR and Mills, SJ and Housely, RM and Spratt, J and Welch, MD and Coolbaugh, MF and Marty, J and Chorazewicz, M and Ferraris, C, The crystal structures of the mixed-valence tellurium oxysalts tlapallite, (Ca,Pb)3CaCu6[Te34+Te6+O12]2(Te4++O3)2(SO4)2 3H2O, and carlfriesite, CaTe24+Te6+O8, Mineralogical Magazine, 83, (4) pp. 539 - 549. ISSN 1471-8022 (2019) [Refereed Article]
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Abstract
The crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space group P321, with a = 9.1219(17) Å, c = 11.9320(9) Å and V = 859.8(3) Å3, and was refined to R1 = 0.0296 for 786 reflections with I > 2σ(I). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, or more simply (Ca,Pb)3CaCu6Te4+8Te6+2O30(SO4)2·3H2O, from H6(Ca,Pb)2(Cu,Zn)3(TeO3)4(TeO6)(SO4). The tlapallite structure consists of layers containing distorted Cu2+O6 octahedra, Te6+O6 octahedra and Te4+O4 disphenoids (which together form the new mixed-valence phyllotellurate anion [Te4+3Te6+O12]12−), Te4+O3 trigonal pyramids and CaO8 polyhedra. SO4 tetrahedra, Ca(H2O)3O6 polyhedra and H2O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4+ and 6+ oxidation states with a known crystal structure, the other being carlfriesite, CaTe4+2Te6+O8. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined to R1 = 0.0230 for 874 reflections with I > 2σ(I). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te4+ secondary bonding.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | tlapallite, crystal structure, tellurate, tellurite, mixed-valence tellurium, carlfriesite, oxysalt, Wildcat prospect, Moctezuma |
| Research Division: | Earth Sciences |
| Research Group: | Geology |
| Research Field: | Mineralogy and crystallography |
| Objective Division: | Mineral Resources (Excl. Energy Resources) |
| Objective Group: | Other mineral resources (excl. energy resources) |
| Objective Field: | Other mineral resources (excl. energy resources) not elsewhere classified |
| UTAS Author: | Missen, OP (Dr Owen Missen) |
| ID Code: | 154954 |
| Year Published: | 2019 |
| Web of Science® Times Cited: | 6 |
| Deposited By: | CODES ARC |
| Deposited On: | 2023-01-20 |
| Last Modified: | 2023-01-25 |
| Downloads: | 0 |
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