Monsmedite discreditation

Johan, Z., G. Udubasa, and J. Zemann (2009): "Monsmedite", a discredited potassium thallium sulphate mineral from Baia Sprie and its identity with voltaite: The state of the art. Neues Jahrbuch fur Mineralogie - Abhandlungen 186(1), 63-66 (2009)

Abstract:

"Monsmedite" was described half a century ago as a new potassium thallium sulphate mineral occurring in Baia Sprie, Romania. It was reported to occur as very dark green, morphologically cubic crystals with idealized formula Tl₂O₃.K₂O.8SO₃ .15H₂O. Many of the data published are close to those of usual voltaite, but the chemical composition and the measured density are clearly different. Up to now, all samples labelled "monsmedite" in mineral collections [including a co-type specimen of "monsmedite"] proved to be usual voltaite with only very minor amounts of thallium. On this basis, and because the original "monsmedite" sample has gone lost, the Commission on New Minerals and Minerals Names of IMA decided to discredit "monsmedite" as a new mineral and to recommend that the name should be reserved for a possible find of a specimen that fulfills the description and chemical composition of "monsmedite".

reference added.



Edited 1 time(s). Last edit at 07/20/2009 08:51PM by Jim Ferraiolo.

Sending Monsmedite to purgatory is a nice touch. Can they do that with Dienerite and Horsfordite?

Dienerite and horsfordite were discredited by IMA 2006-C.

Dienerite = dienerite (Ni3As) = nickelskutterudite (NiAs3) because of an error in publishing the composition; no crystallographic or optical data available; original specimen lost.

Horsfordite = metallurgical(?) mixture of three phases; in the artificial system Cu-Sb, the stable compounds are Cu2Sb and Cu3Sb; Cu11Sb2 appears to be an unstable high-temperature phase (holotype lost).


Monsmedite was originally approved by CNMMN (1971), but later discredited by CNMMN (IMA 1998-D).



Edited 1 time(s). Last edit at 07/21/2009 07:54AM by Marco E. Ciriotti.

Thanks so much Marco. And a great big thank you to whomever took the time to do these discreditations!!! Soon I'll have nothing to rant about.

Results reported in
Kovács-Pálffy, P. et al. (2009): Re-examination of "Monsmedite" from the type locality Baia Sprie, Baia Mare district (Romania). Mitt. Österr. Mineral. Ges. 155, 88. (Abs.)
show that the Tl2O3 content varies from 1.69-3.12 wt% (it is not stated why the presence of Tl+ is excluded). According to Mößbauer spectroscopy all Fe is trivalent, unlike voltaite.

If the Fe(III) result is reproducible, then it can't be synonymous with voltaite and resubmission (and renaming) will be necessary.