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The minerals boulangerite, falkmanite and Cu-free meneghinite; synthesis, new powder diffraction data and stability relations

Kamal L. Pruseth, Biswajit Mishra and Heinz-Juergen Bernhardt
The minerals boulangerite, falkmanite and Cu-free meneghinite; synthesis, new powder diffraction data and stability relations
European Journal of Mineralogy (April 2001) 13 (2): 411-419

Abstract

Although falkmanite of the ideal composition proposed by Ramdohr & Odman (1940), Pb (sub 3) Sb (sub 2) S (sub 6) , could not be synthesized even with the help of halide fluxes, a phase with composition similar to boulangerite, (Pb (sub 5) Sb (sub 4) S (sub 11) ) but with dissimilar X-ray diffraction pattern was synthesized by sulfidation of bournonite at 400 and 500 degrees C. This phase has been provisionally referred to as falkmanite in this study. Molar PbS:Sb (sub 2) S (sub 3) ratio in boulangerite varied from 2.41 to 2.47 and that in falkmanite varied from 2.51 to 2.57. Powder X-ray-diffraction pattern for boulangerite furnished an orthorhombic cell with a = 23.443 Aa, b = 21.183 Aa and c = 4.505 Aa, while that for falkmanite gave a monoclinic cell with a = 21.626 Aa, b = 11.409 Aa, c = 7.876 Aa and beta = 96.19 degrees . This raises doubts as to the identity of falkmanite as a member of the boulangerite homologous series, as proposed by Mozgova et al. (1983). At 530 degrees C, Cu-free meneghinite co-existed with falkmanite, signifying that the meneghinite solid solution field in the ternary Cu (sub 2) S-PbS-Sb (sub 2) S (sub 3) touched the PbS-Sb (sub 2) S (sub 3) binary between 500 and 530 degrees C. From 530 to 560 degrees C, the proportion of Cu-free meneghinite gradually increased relative to that of falkmanite implying increased overlap of the meneghinite solid solution field with the PbS-Sb (sub 2) S (sub 3) binary. Falkmanite and boulangerite synthesized at 500 degrees C and heated at 560 degrees C for 2 hours provided similar X-ray-diffraction patterns, which corresponded with that of Cu-free meneghinite.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 13
Serial Issue: 2
Title: The minerals boulangerite, falkmanite and Cu-free meneghinite; synthesis, new powder diffraction data and stability relations
Affiliation: Universitaet zu Koeln, Institut fuer Mineralogie und Geochemie, Koln, Federal Republic of Germany
Pages: 411-419
Published: 200104
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 25
Accession Number: 2001-049322
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
Secondary Affiliation: Indian Institute of Technology, IND, IndiaRuhr Universitaet, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200115
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