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What is the reason for the doubled unit-cell volumes of copper-lead-rich pavonite homologues? The crystal structures of cupromakovickyite and makovickyite

Dan Topa, Emil Makovicky and Tonci Balic-Zunic
What is the reason for the doubled unit-cell volumes of copper-lead-rich pavonite homologues? The crystal structures of cupromakovickyite and makovickyite
The Canadian Mineralogist (April 2008) 46 (2): 515-523

Abstract

The crystal structure of cupromakovickyite, ideally Cu (sub 8) Pb (sub 4) Ag (sub 2) Bi (sub 18) S (sub 36) , from the skarn deposit at Baita Bihor, in Romania, has been solved by direct methods and refined to an R (sub 1) index of 5.36% for 2680 unique reflections measured with MoKalpha radiation on a four-circle diffractometer equipped with a CCD detector. Cupromakovickyite has a monoclinic cell with a 13.405(8), b 4.016(3), c 29.949(19) Aa, beta 99.989(16), V 1587.8(17) Aa (super 3) , space group C2/m and Z = 1. There are eight metal sites and twelve sulfur sites in each of the four asymmetric units. The thicker, galena-like layers are composed of parallel chains Bi4-Bi1-Bi1-Bi4 four octahedra long. In the thinner layers, the octahedra of Ag are replaced by two tetrahedrally coordinated Cu sites, whereas one of the paired square pyramids of Bi is replaced by Pb. The asymmetry of the thin layer is responsible for the doubling of the c parameter for cupromakovickyite with respect to makovickyite. To be able to compare them, the crystal structure of Cu-bearing makovickyite, Cu (sub 2.25) Ag (sub 1.56) (Pb (sub 0.27) Cd (sub 0.13) ) (sub Sigma 0.4) Bi (sub 10.46) S (sub 18) , from a scheelite deposit at Felbertal, in Austria, has been refined to an R (sub 1) index of 4.36% for 1320 unique reflections measured with the same equipment. Makovickyite has a monoclinic cell with a 13.239(3), b 4.0547(7), c 14.667(3) Aa, beta 99.397(4), V 776.7(3) Aa (super 3) , space group C2/m and Z = 1. There are four metal sites and six sulfur sites in each of the four asymmetric units. The thicker, galena-like layers are composed of parallel chains Bi2-Bi1-Bi1-Bi2 four octahedra long. In the thinner layers, the octahedra of Ag are partially replaced by two tetrahedrally coordinated Cu sites.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 46
Serial Issue: 2
Title: What is the reason for the doubled unit-cell volumes of copper-lead-rich pavonite homologues? The crystal structures of cupromakovickyite and makovickyite
Affiliation: University of Salzburg, Department of Materials Research & Physics, Salzburg, Austria
Pages: 515-523
Published: 200804
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 19
Accession Number: 2008-102393
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Secondary Affiliation: University of Copenhagen, DNK, Denmark
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200835
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