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Claraite, (Cu,Zn) (sub 15) (AsO (sub 4) ) (sub 2) (CO (sub 3) ) (sub 4) (SO (sub 4) )(OH) (sub 14) .7H (sub 2) O; redefinition and crystal structure

Cristian Biagioni and Paolo Orlandi
Claraite, (Cu,Zn) (sub 15) (AsO (sub 4) ) (sub 2) (CO (sub 3) ) (sub 4) (SO (sub 4) )(OH) (sub 14) .7H (sub 2) O; redefinition and crystal structure
European Journal of Mineralogy (June 2017) 29 (6): 1031-1044

Abstract

Since the beginning of the 2000s, several authors reported the occurrence of As and S as chemical components of the hydrated copper hydroxy-carbonate claraite, originally described with the formula (Cu,Zn) (sub 3) (CO (sub 3) )(OH) (sub 4) .4H (sub 2) O. Owing to the lack of knowledge about the crystal structure of this mineral, the structural role played by these chemical elements was unknown. The crystal structure of claraite has now been solved from single-crystal X-ray diffraction data by using a specimen from the marble quarries of Carrara, Apuan Alps, Tuscany, Italy. Electron-microprobe analyses gave (in wt% - average of eight spot analyses): SO (sub 3) 4.00, As (sub 2) O (sub 5) 13.16, CuO 52.64, ZnO 9.03, CO (sub 2(calc)) 9.08, H (sub 2) O (sub (calc)) 12.56, total 100.47. On the basis of 15 (Cu + Zn) and 45 O atoms per formula unit, the chemical formula of claraite could be written as (Cu (sub 12.85) Zn (sub 2.15) ) (sub Sigma 15.00) (AsO (sub 4) ) (sub 2.22) (CO (sub 3) ) (sub 4) (SO (sub 4) ) (sub 0.97) (OH) (sub 13.40) .6.83H (sub 2) O, ideally (Cu,Zn) (sub 15) (AsO (sub 4) ) (sub 2) (CO (sub 3) ) (sub 4) (SO (sub 4) )(OH) (sub 14) .7H (sub 2) O. Raman spectrometry shows bands related to bending and stretching vibrations of AsO (sub 4) and SO (sub 4) groups, as well as the stretching mode of CO (sub 3) groups and O-H bonds. The unit-cell parameters of claraite are a = 10.3343(6)A, b = 12.8212(7)A, c = 14.7889(9)A, alpha = 113.196(4) degrees , beta = 90.811(4) degrees , gamma = 89.818(4) degrees , V = 1800.9(2) A (super 3) , space group P1. The crystal structure has been refined to R (sub 1) = 0.111 on the basis of 6956 reflections with F (sub o) > 4sigma (F (sub o) ) and 363 refined parameters. Claraite shows a layered structure, with {001} heteropolyhedral layers formed by CuPhi (sub 5) and CuPhi (sub 6) polyhedra as well as AsO (sub 4) and CO (sub 3) groups. These layers are stacked along c through edge-sharing Cu (sub 2) Phi (sub 10) and Cu (sub 2) Phi (sub 8) dimers, the former being decorated by corner-sharing SO (sub 4) groups hosted within intra-framework channels together with H (sub 2) O groups. Claraite is the only known mineral showing the simultaneous occurrence of essential AsO (sub 4) , CO (sub 3) , and SO (sub 4) groups.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 29
Serial Issue: 6
Title: Claraite, (Cu,Zn) (sub 15) (AsO (sub 4) ) (sub 2) (CO (sub 3) ) (sub 4) (SO (sub 4) )(OH) (sub 14) .7H (sub 2) O; redefinition and crystal structure
Affiliation: Universita di Pisa, Dipartimento di Scienze della Terra, Pisa, Italy
Pages: 1031-1044
Published: 20170628
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 38
Accession Number: 2017-082608
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 9 tables
N42°19'60" - N44°19'60", E09°40'00" - E12°25'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201743
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