Affioramento metallifero ad arseniati e solfati a debole radioattività: Rio Spinal da Ciare (Cercivento-Udine)

Among the specimens of the mineralogical collection of Claudio Calligaris, entrusted to the Friulian Museum of Natural History after his untimely death, there are some samples from the Permian levels of the Val Gardena Sandstone, that present weak levels of radioactivity. The presence of radioactive minerals is relatively common in the outcrops of this formation throughout the Sudalpine area and for this reason, a few decades ago, some prospectings were carried out to verify its possible exploitation. In addition to the outcrop indicated in the Calligaris collection (Rio Minischitte, Paularo), similar levels have been identified in the area between Ravascletto and Cercivento: on these, more detailed research and some mineralogical analyses have been carried out on the collected samples: the presence of about thirty mineralogical species has been highlighted, none of which, however, is “radioactive”: as in other areas, the weak radioactivity detected comes from the adsorption of microscopic uranium particles onto organic matter (plant remains). Among the ascertained species, the following should be noted: anglesite, arsenolite, brochantite, chenevixite, cornwallite, devillin, langitis, mimetite, olivenitis, parnauite, richelsdorfite, scorodite, tennantite, tangdanite, tyrolite, zalesiite.