Nollmotzite

nollmotzite

richetite

wyartite

shinkolobweite

Images

Formula: Mg[U5+(U6+O2)2O4F3].4H2O
Oxide
Colour: Deep violet-brown
Luminescence: Non-fluorescent under long wave and short wave UV
RADIOACTIVE
Environments

Sedimentary environments
Hydrothermal environments

Nollmotzite is a relatively new mineral, approved in 2018 and to date (June 2022) reported only from the type locality. It is one of the very few mineral species with pentavalent uranium U5+, together with richetite, wyartite, and shinkolobweite. It is the first natural uranium oxide containing fluorine that has been found.

Localities

At the type locality, the Clara mine, Oberwolfach, Wolfach, Ortenaukreis, Freiburg Region, Baden-Württemberg, Germany, nollmotzite occurs in cavities in quartz gangue with abundant dark violet to black fluorite and baryte. It forms deep violet-brown thin prisms up to ~0.3 mm, with chisel-like terminations.
The presence of fluorine and pentavalent uranium in the structure of nollmotzite has potentially important implications for the safe disposal of nuclear waste (AM 106.163).
Nollmotzite is formed by precipitation from uranium-containing aqueous solutions under partially reducing conditions, most probably enhanced by consumption of oxygen during the oxidation of abundant pyrite present in the gangue (HOM).

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