Uranium mineralisation in Permian schists (Briançonnais Domain).

Traces of uranium phosphates were observed on the surface. In 1958 about 200 m of exploration galleries were excavated by SoMiREn (a mining company owned by ENI).

The primary mineralization, probably because of its scarcity, has never been observed and the mineralized veins are made up of coatings of alteration minerals (autunite and torbernite) that cover the interstices of the schist.

Anatase: present as rare submillimeter black bipyramids.

Autunite: is the most abundant uranium alteration mineral, and is present mainly in very thin blades, with an undefined outline and pale yellow in color. More rarely, it is found in the schist as microscopic well-formed crystals of square tabular habitus and pale yellow in color.

Baryte: found as tabular crystals.

Fluorite: is very common, both inside and outside the mine, inside white quartzite veins as purple and deep purple (almost black) masses, more rarely it forms cubic and even more rarely octahedral crystals!

Gypsum: is very common in the lower parts of the tunnels inside the mine, and it is of neoformation since it encrusts the excavated walls of the mine. It sometimes forms nice aggregates of crystals of monoclinic habitus.

Pyrite: present as microscopic cubes inside the metemorphosed porphyroid. The weathering of this microscopic cubes causes the rocks to be reddish/brown in color.

Torbernite: Rarer than autunite, it usually forms flattened crystals of a pale grass green, in one occurrence it has been found as green tabular crystals with a core of autunite.
Rarely, it can be found as crystals with a defined outline, sometimes large (5 mm), in which the intense green has remained unchanged thanks to a very fine veil of gypsum.
Even more rarely it has been found as minute crystals with bipyramidal habitus, sharp and well-formed.

Other Regions, Features and Areas containing this locality

References