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Re-investigations of minerals first described from the Carpathian Region

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Gábor Papp
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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: K1.52–1.77Tl+0.23–0.33Fe2+1.79–1.91Mn2+0.84–2.16Zn2+0.51–0.64Mg2+0.06–2.03Fe3+2.63–2.82Al3+1.01–1.50(SO4)11.92–12.1615.52–17.72H2O
Gábor Papp
added 2 research items
Five specimens of "dognacskaite" from Dognecea (Caras-Severin County, Banat, Romania), a poorly described substance, once considered a Cu-Bi sulfosalt, were studied by ore microscopy, SEM, EPMA, and XRPD methods. One of the specimens is probably that used for the original description by Jozsef Krenner. Every specimen proved to be a mixture with a similar mineral composition and texture. The main component of "dognacskaite" is bismuthinite rimmed by wittichenite (containing strings of native bismuth), the latter is in turn rimmed by copper sulfides (mainly djurleite with some covellite). Emplectite can also be found occasionally in the larger voids of bismuthinite. Magnetite (in some cases oxidized), chalcopyrite, bornite (replacing chalcopyrite) and rare sphalerite and tetradymite form inclusions in bismuthinite or in the rims surrounding it. Goethite, calcite, bismuth ochre and other unspecified fine-grained products of alteration are abundant in the voids. Data from earlier studies are easily explainable on the basis of this mineral assemblage, suggesting that every specimen of "dognacskaite" is a mixture of this kind. The samples may correspond to a (pyrite-) magnetite-chalcopyrite skarn ore replaced by a post-skarn hydrothermal bismuthinite ore, later affected by supergene copper enrichment then by oxidation processes. The exact locality of "dognacskaite" cannot be determined, but at least some of the specimens have been collected in the former Petri-Pauli (or Peter-Pal), now Petru si Pavel mine on Mt. Danilii.
Original parajamesonite samples of Zsivny & Náray-Szabó (1947) and other authentic museum specimens containing the same material were studied by ore microscopy, electron probe microanalysis (EPMA) and X-ray powder diffraction (XRPD). The “parajamesonite crystals” proved to be pseudomorphs built of polycrystalline aggregates of euhedral jamesonite, sometimes intergrown with argentian tetrahedrite (freibergite) and/or ramdohrite. Other associated minerals are “plumosite”, i.e. fibrous jamesonite (rarely with boulangerite), iron-rich sphalerite, siderite, pyrrhotite, semseyite, a fizélyite-related mineral, and galena. All XRPD patterns correspond to jamesonite, without any similarity to the original pattern of parajamesonite. All these data prove that parajamesonite is actually jamesonite, permitting to discredit definitively parajamesonite as a mineral species.