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Cervelleite, Ag4tes: Solution and Description of the Crystal Structure

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Cervelleite, Ag4tes: Solution and Description of the Crystal Structure Geological and Atmospheric Sciences Publications Geological and Atmospheric Sciences 8-2015 Cervelleite, Ag4TeS: solution and description of the crystal structure L. Bindi Università di Firenze C. J. Stanley Natural History Museum Paul G. Spry Iowa State University, [email protected] Follow this and additional works at: https://lib.dr.iastate.edu/ge_at_pubs Part of the Geology Commons, and the Mineral Physics Commons The complete bibliographic information for this item can be found at https://lib.dr.iastate.edu/ ge_at_pubs/350. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Geological and Atmospheric Sciences at Iowa State University Digital Repository. It has been accepted for inclusion in Geological and Atmospheric Sciences Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Cervelleite, Ag4TeS: solution and description of the crystal structure Abstract Examination of the type specimen of cervelleite throws new light on its structure demonstrating how earlier researchers erred in describing the mineral as cubic. It was found to be monoclinic, space group P21/n, with a = 4.2696(4), b = 6.9761(5), c = 8.0423(7) Å, β = 100.332(6)°, V = 235.66(3) Å3, Z = 4. The crystal structure [R1 = 0.0329 for 956 reflections with I > 2σ(I)] is topologically identical to that of acanthite, Ag2S, and aguilarite, Ag4SeS. It can be described as a body-centered array of tetrahedrally coordinated X atoms (where X = S and Te) with Ag2X4 polyhedra in planes nearly parallel to (010); the sheets are linked by the other silver position (i.e., Ag1) that exhibits a three-fold coordination. Crystal- chemical features are discussed in relation to other copper and silver sulfides/tellurides, and pure metals. A SEM study of the cervelleite crystal used for the structural investigation showed that it is intergrown with an unnamed Ag2FeS2 phase in the type material. Keywords cervelleite, Ag-Te-S system, Ag-Cu sulfotellurides, crystal structure, aguilarite, acanthite Disciplines Geology | Mineral Physics Comments This is a manuscript of an article published as Bindi, L., Stanley, C.J. & Spry, P.G. Cervelleite, Ag4TeS: solution and description of the crystal structure. Miner Petrol 109, 413–419 (2015). doi:10.1007/ s00710-015-0384-4. Posted with permission. This article is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/ge_at_pubs/350 Mineralogy and Petrology Cervelleite, Ag4TeS: solution and description of the crystal structure --Manuscript Draft-- Manuscript Number: MIPE-D-15-00008R1 Full Title: Cervelleite, Ag4TeS: solution and description of the crystal structure Article Type: Standard Article Keywords: cervelleite; Ag-Te-S system; Ag-Cu sulfotellurides; crystal structure; aguilarite; acanthite Corresponding Author: Luca Bindi, Prof University of Florence Florence, ITALY Corresponding Author Secondary Information: Corresponding Author's Institution: University of Florence Corresponding Author's Secondary Institution: First Author: Luca Bindi, Prof First Author Secondary Information: Order of Authors: Luca Bindi, Prof Christopher Stanley Paul G Spry Order of Authors Secondary Information: Funding Information: Abstract: Examination of the type specimen of cervelleite throws new light on its structure demonstrating how earlier researchers erred in describing the mineral as cubic. It was found to be monoclinic, space group P21/n, with a = 4.2696(4), b = 6.9761(5), c = 8.0423(7) Å, β = 100.332(6)°, V = 235.66(3) Å3, Z = 4. The crystal structure [R1 = 0.0329 for 956 reflections with I > 2σ(I)] is topologically identical to that of acanthite, Ag2S, and aguilarite, Ag4SeS. It can be described as a body-centered array of tetrahedrally coordinated X atoms (where X = S and Te) with Ag2X4 polyhedra in planes nearly parallel to (010); the sheets are linked by the other silver position (i.e., Ag1) that exhibits a three-fold coordination. Crystal-chemical features are discussed in relation to other copper and silver sulfides/tellurides, and pure metals. A SEM study of the cervelleite crystal used for the structural investigation showed that it is intergrown with an unnamed Ag2FeS2 phase in the type material. Response to Reviewers: Dear Anton, Please find herewith the revised copy of the manuscript entitled “Cervelleite, Ag4TeS: solution and description of the crystal structure” by Luca Bindi, Christopher J. Stanley, and Paul G. Spry. We did the minor stylistic changes suggested by the reviewers. We think that it is not necessary to add the Table as suggested by Rev#2. With best regards, Luca Bindi Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Manuscript Click here to download Manuscript: MIPE-D-15-00008_text.doc 1 1 2 3 4 5 6 7 8 Cervelleite, Ag4TeS: solution and description of the crystal 9 10 structure 11 12 13 14 15 L. Bindi a C.J. Stanley b P.G. Spry c 16 17 18 19 20 21 a 22 Dipartimento di Scienze della Terra, Università di Firenze, Via G. La Pira 4, I-50121Firenze, Italy 23 24 b 25 Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, United 26 27 Kingdom 28 29 c 30 Department of Geological and Atmospheric Sciences, 253 Science I, Iowa State University, Ames, 31 Iowa 50011-3212, U.S.A. 32 33 34 35 36 37 38 Corresponding author: 39 40 Luca Bindi 41 42 Dipartimento di Scienze della Terra, 43 Università di Firenze 44 Via G. La Pira 4, I-50121 Firenze, Italy 45 46 Tel. +39-055-2757532 47 Fax +39-055-2757455 48 49 e-mail: [email protected] 50 51 52 53 54 55 Keywords: cervelleite Ag-Te-S system - crystal structure 56 57 aguilarite acanthite 58 59 60 61 62 63 64 65 2 Abstract 1 2 3 Examination of the type specimen of cervelleite throws new light on its structure 4 5 demonstrating how earlier researchers erred in describing the mineral as cubic. It 6 7 was found to be monoclinic, space group P2 /n, with a = 4.2696(4), b = 6.9761(5), c 8 1 9 3 10 = 8.0423(7) Å, β = 100.332(6)°, V = 235.66(3) Å , Z = 4. The crystal structure [R1 = 11 12 0.0329 for 956 reflections with I > 2σ(I)] is topologically identical to that of acanthite, 13 14 15 Ag2S, and aguilarite, Ag4SeS. It can be described as a body-centered array of 16 17 tetrahedrally coordinated X atoms (where X = S and Te) with Ag2X4 polyhedra in 18 19 20 planes nearly parallel to (010); the sheets are linked by the other silver position (i.e., 21 22 Ag1) that exhibits a three-fold coordination. Crystal-chemical features are discussed 23 24 25 in relation to other copper and silver sulfides/tellurides, and pure metals. A SEM 26 27 study of the cervelleite crystal used for the structural investigation showed that it is 28 29 intergrown with an unnamed Ag FeS phase in the type material. 30 2 2 31 32 33 34 35 Introduction 36 37 Silver chalcogenides have received much attention in recent years because of 38 39 40 their important technological applications (e.g., Padma Kumar and Yashonath 2006). 41 42 These compounds are known to be fast ionic conductors or semiconductors and, as 43 44 such, find practical applications in silver photography as sensitizers or in optics and 45 46 47 microelectronics as rewritable storage media. From a geological standpoint, silver 48 49 sulfotellurides are trace constituents accompanying native gold and Au-Ag-tellurides 50 51 52 in various deposit types that span the magmatic-hydrothermal spectrum. 53 54 In the system Ag-Te-S, cervelleite Ag4TeS is of particular interest because it 55 56 57 occurs as an accessory mineral in a range of hydrothermal precious mineral deposits 58 59 (Cook and Ciobanu 2003). It was defined as a new mineral species by Criddle et al. 60 61 62 63 64 65 3 (1989) during a study of ore minerals collected from the spoil tips of the abandoned 1 2 Bambolla mine, Moctezuma, Sonora (Mexico). By means of X-ray photographic 3 4 5 techniques, these authors studied fragments of cervelleite intergrown with acanthite 6 7 from a structural point of view and reported a cubic symmetry (with P23, Pm3, P432, 8 9 10 P43m, Pm3m, P213, P4232, P4132, P4332, Pa3 as possible space groups) with a = 11 12 14.03(1) and Z = 24. Criddle et al. (1989) also noticed that cervelleite, acanthite and 13 14 hessite were altered rapidly and profoundly by light, in a surface reaction interpreted 15 16 17 as photo-chemical in origin. 18 19 Cervelleite, along with other cervelleite-like minerals, has been reported from 20 21 22 various ore types including the intrusion-hosted San Martin deposit, Argentina (Paar 23 24 and De Brodtkorb 1996), the epithermal Mayflower Au-Ag deposit, Montana (Spry 25 26 27 and Thieben 1996), the Um Samiuki volcanogeneic massive sulfide deposit, Egypt 28 29 (Helmy 1999), epithermal (Larga, Roşia Montană) and skarn (Băiţa Bihor and Ocna 30 31 de Fier) occurrences in Romania (Cook and Ciobanu 2003; Ciobanu et al. 2004), the 32 33 34 Eniovche epithermal deposit, Bulgaria (Dobrev et al. 2002), the intrusion-hosted 35 36 Funan Au deposit, China (Gu et al. 2003), and several volcanic-hosted massive 37 38 39 sulfide deposits in the southern Urals (Novoselov et al. 2006). Unnamed Ag- 40 41 sulfotellurides [(Ag,Cu)6TeS2 – (Ag,Cu)4TeS] were described from the Funan deposit 42 43 44 (Gu et al. 2003), and a phase with the composition Ag2Cu2TeS was reported by Cook 45 46 and Ciobanu (2003) from the Băiţa Bihor and Ocna de Fier skarns in Romania.
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