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Chenite, Pb4Cu(SO4)2(OH)6, a new mineral, from Leadhills, Scotland

Published online by Cambridge University Press:  05 July 2018

W. H. Paar
Affiliation:
Institut für Geowissenschaften (Mineralogie) der Universität Salzburg, Akademiestrasse 26, A-5020 Salzburg, Austria
Kurt Mereiter
Affiliation:
Institut für Mineralogie, Kristallographie und Strukturchemie der Technischen Universität Wien, Getreidemarkt 9, A-1060, Wien, Austria
R. S. W. Braithwaite
Affiliation:
Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M60 1QD England
Paul Keller
Affiliation:
Institut für Mineralogie und Kristallchemie der Universität Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80, Federal Republic of Germany
P. J. Dunn
Affiliation:
Department of Mineral Sciences, Smithsonian Institution, Washington, DC, USA 20560

Abstract

Chenite, a new lead-copper secondary mineral, has been found on specimens from the Leadhills area, Scotland. It is associated with caledonite, linarite, leadhillite, susannite, and other species, on oxidized galena with chalcopyrite. Electron microprobe analysis yielded PbO 74.5, CuO 7.8, SO3 13.3, H2O 4.4 (by difference), sum = 100 wt. %. The empirical formula (based on 14 oxygens) is Pb3.98Cu1.17S1.98O14H5.82; the ideal formula is Pb4Cu(SO4)2(OH)6, which requires PbO 75.2, CuO 6.7, SO3 13.5, H2O 4.6, sum = 100 wt. %.

Infra-red spectroscopy showed the presence of only and OH ions, with no H2O.

Chenite is triclinic, P1 or P̄, with a = 5.791(1), b = 7.940(1), c = 7.976(1) Å, α = 112.02(1), β = 97.73(1), γ = 100.45(1)°, V = 326.0 Å3, Z = 1. The strongest lines in the X-ray powder diffraction pattern (d, I/Io, hkl) are: 5.55, 7, 100; 4.32, 6, 11; 3.60, 10 002; 3.41, 9, 10; 3.30, 5, 02; 3.00, 5, 111; 2.80, 7, 12; 2.07, 6, 211/21/13; 1.778, 5, 3/23.

Chenite forms minute, singly terminated, transparent to translucent sky-blue crystals from 0.1 to over 1 mm long, elongated approximately [032]. Twenty different forms (pinacoids) have been identified on the four crystals studied. A good cleavage on {100}, and traces of a second on {001}, can be observed. Optically, chenite is biaxial negative, 2 V(measured) = 67±1°, 2 V(calc.) = 68° (Na). The refractive indices are α 1.871±0.005, β 1.909±0.005, γ 1.927±0.005 (Na). Dispersion is strong, r≫v. The mineral is weakly pleochroic. H (Mohs) ∼ 2½. D = 5.98, and calculated Dx = 6.044 g cm−3.

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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