Eliopoulosite, V7S8, A New Sulfide from the Podiform Chromitite of the Othrys Ophiolite, Greece

Autor: Basilios Tsikouras, Giorgio Garuti, Paola Bonazzi, Tassos A. Grammatikopoulos, Federica Zaccarini, Luca Bindi, Chris J. Stanley
Rok vydání: 2020
Předmět:
Zdroj: Minerals
Volume 10
Issue 3
Minerals, Vol 10, Iss 3, p 245 (2020)
ISSN: 2075-163X
Popis: The new mineral species, eliopoulosite, V7S8, was discovered in the abandoned chromium mine of Agios Stefanos of the Othrys ophiolite, located in central Greece. The investigated samples consist of massive chromitite hosted in a strongly altered mantle tectonite, and are associated with nickelphosphide, awaruite, tsikourasite, and grammatikopoulosite. Eliopoulosite is brittle and has a metallic luster. In plane-reflected polarized light, it is grayish-brown and shows no internal reflections, bireflectance, and pleochroism. It is weakly anisotropic, with colors varying from light to dark greenish. Reflectance values of mineral in air (Ro, Re&rsquo
in %) are: 34.8&ndash
35.7 at 470 nm, 38&ndash
39 at 546 nm, 40&ndash
41.3 at 589 nm, and 42.5&ndash
44.2 at 650 nm. Electron-microprobe analyses yielded a mean composition (wt.%) of: S 41.78, V 54.11, Ni 1.71, Fe 1.1, Co 0.67, and Mo 0.66, totali 100.03. On the basis of &Sigma
atoms = 15 apfu and taking into account the structural data, the empirical formula of eliopoulosite is (V6.55Ni0.19Fe0.12Co0.07Mo0.04)&Sigma
= 6.97S8.03. The simplified formula is (V, Ni, Fe)7S8 and the ideal formula is V7S8, which corresponds to V 58.16%, S 41.84%, total 100 wt.%. The density, based on the empirical formula and unit-cell volume refined form single-crystal structure XRD data, is 4.545 g·
cm&minus
3. The mineral is trigonal, space group P3221, with a = 6.689(3) Å
c = 17.403(6) Å
V = 674.4(5) Å
3, Z = 3, and exhibits a twelve-fold superstructure (2a ×
2a ×
3c) of the NiAs-type subcell with V-atoms octahedrally coordinated by S atoms. The distribution of vacancies is discussed in relation to other pyrrhotite-like compounds. The mineral name is for Dr. Demetrios Eliopoulos (1947&ndash
2019), a geoscientist at the Institute of Geology and Mineral Exploration (IGME) of Greece and his widow, Prof. Maria Eliopoulos (nee Economou, 1947), University of Athens, Greece, for their contributions to the knowledge of ore deposits of Greece and to the mineralogical, petrographic, and geochemical studies of ophiolites, including the Othrys complex. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association (No. 2019-96).
Databáze: OpenAIRE
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