Péter KOVÁCS-PÁLFFY¹, József MUSKE², Mária FÖLDVÁRI¹, Péter KÓNYA¹, Zoltán HOMONNAY³, Theodoros NTAFLOS⁴, Gábor PAPP⁵, Edit KIRÁLY1, István SAJÓ⁶, Veronika SZILÁGYI⁷ & Gábor BOZSÓ⁸
1 - Geological Institute of Hungary, H-1143, Budapest, Stefánia út 14, Hungary, e-mail: kovacs@mafi.hu, kope@mafi.hu, foldvari@mafi.hu
2 – 90443-Nürnberg, Knauerstrasse 9, Germany, e-mail: JMuske@arcor.de
3 - Department of Nuclear Chemistry, Eötvös Loránd University, H-1117, Budapest, Pázmány P. sétány 1/A, Hungary, e-mail: homonnay@ludens.elte.hu
4 - Department of Lithospheric Research, University of Vienna, Althahnstrasse 14, 1090-Wien, Austria, e-mail: theodoros.ntaflos@univie.ac.at
5 - Hungarian Natural History Museum, Department of Mineralogy and Petrology, Pf. 137, H-1431 Budapest, e-mail: pappmin@ludens.elte.hu
6 - Chemical Research Centre of the Hungarian Academy of Sciences, H-1025 Budapest, Pusztaszeri út 59-67, Hungary, e-mail: sajo@chemres.hu
7 - Department of Nuclear Research Institute of Isotopes, Hungarian Academy of Sciences, Budapest, Hungary, e-mail: szilagyiv@iki.kfki.hu
8 – Department of Mineralogy, Geochemistry and Petrology, University of Szeged, H-6721 Szeged, P.O. Box 951, e-mail: bozso.gabor@geo.u-szeged.hu


DETAILED STUDY OF “MONSMEDITE” SPECIMENS FROM THE ORIGINAL (1963) FIND, BAIA SPRIE, BAIA MARE ORE DISTRICT (ROMANIA)

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“Monsmedite”, originally described as a unique, Tl(III)-rich mineral of Tl₂O₃·K₂O·8SO₃·15H₂O formula from Baia Sprie, Romania, was reinvestigated using authentic specimens from the original finder of the mineral. “Monsmedite” is discredited as voltaite but the discreditation was based on specimens of unspecified origin, as the type material had been lost. Open questions related to the Tl-content and the limited scope of investigations done prior to the discreditation of “monsmedite” prompted this study. The presented results of the X-ray powder diffraction, thermoanalytical, IR-spectroscopic, Mössbauer spectroscopic, scanning electron microscopic and different kinds of chemical investigations confirmed that our “monsmedite” is Tl(I)-bearing voltaite but revealed a wide variability of Tl-content, reaching up to 7.49 wt% Tl₂O. Empirical formula of “monsmedite” (from full chemical analysis of two samples) is: