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Kapellasite, Cu3Zn(OH)6CI2, a new mineral from Lavrion, Greece, and its crystal structure

Published online by Cambridge University Press:  05 July 2018

W. Krause*
Affiliation:
Henriette-Lott-Weg 8, D-50354 Hürth, Germany
H.-J. Bernhardt
Affiliation:
Institut für Mineralogie, Ruhr-Universität Bochum, Universitätsstraβe 150, D-44780 Bochum, Germany
R.S.W. Braithwaite
Affiliation:
School of Chemistry, Faraday Building, University of Manchester, Manchester M60 1QD, UK
U. Kolitsch
Affiliation:
Institut für Mineralogie und Kristallographie, Universität Wien, Geozentrum, Althanstraβe 14, A-1090 Wien, Austria
R. Pritchard
Affiliation:
School of Chemistry, Faraday Building, University of Manchester, Manchester M60 1QD, UK

Abstract

Kapellasite, Cu3Zn(OH)6Cl2, is a new secondary mineral from the Sounion No. 19 mine, Kamariza, Lavrion, Greece. It is a polymorph of herbertsmithite. Kapellasite forms crusts and small aggregates up to 0.5 mm, composed of bladed or needle-like indistinct crystals up to 0.2 mm long. The colour is green-blue, the streak is light green-blue. There is a good cleavage parallel to ﹛0001﹜. Kapellasite is uniaxial negative, ω = 1.80(1), ε = 1.76(1); pleochroism is distinct, with E = pale green, O = green-blue. Dmeas = 3.55(10) g/cm3; Dcalc. = 3.62 g/cm3. Electron microprobe analyses of the type material gave CuO 58.86, ZnO 13.92, NiO 0.03, CoO 0.03, Fe2O3 0.04, Cl 16.70, H2O (calc.) 12.22, total 101.80, less O = Cl 3.77, total 98.03 wt.%. The empirical formula is (Cu3.24Zn0.75)Σ3.99(OH)5.94Cl2.06, based on 8 anions. The five strongest XRD lines are [d in Å (I/I0, hkl)] 5.730 (100, 001), 2.865 (11, 002), 2.730 (4, 200), 2.464 (9, 021/201), 1.976 (5, 022/202). Kapellasite is trigonal, space group Pml, unit-cell parameters (from single-crystal data) a = 6.300(1), c = 5.733(1) Å, V= 197.06(6) Å3, Z = 1. The crystal structure of kapellasite is based on brucite-like sheets parallel to (0001), built from edge-sharing distorted M(OH,Cl)6 (M = Cu, Zn) octahedra. The sheets stack directly on each other (…AAA… stacking). Bonding between adjacent sheets is only due to weak hydrogen and O…C1 bonds. The name is in honour of Christo Kapellas (1938–2004), collector and mineral dealer from Kamariza, Lavrion, Greece.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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