Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original paper

Martin Števko, Jiří Sejkora, Štefan Ferenc

Supergene uranyl molybdates (calcurmolite, iriginite and umohoite) from the Majerská valley U-Mo occurrence near Čučma, Slovakia: Mineralogy, chemical composition and Raman spectroscopy

Journal of Geosciences, volume 70 (2025), issue 3, 139 - 150

DOI: http://doi.org/10.3190/jgeosci.0043.25

A new occurrence of three rare supergene uranyl molybdates, calcurmolite, iriginite and umohoite was recently discovered at the Majerská valley U-Mo prospect near Čučma, Spišsko-gemerské rudohorie Mts., Slovakia. Calcurmolite is the most common uranyl molybdate at the studied locality, followed by relatively common iriginite and rare umohoite. In this paper, we present their detailed mineralogical study, including paragenetic observations, X-ray powder diffraction, chemical composition, and a Raman spectroscopic study. The quantitative chemical (WDS) data indicate a significant presence of Fe (around 0.35 apfu) in both iriginite and umohoite, whereas Na and K are typical minor elements observed in calcurmolite. The studied assemblage of supergene uranyl molybdates was formed by in-situ weathering of uraninite-molybdenite aggregates under the relatively acidic conditions, caused by breakdown of abundant pyrite and absence of carbonates.