Isabella Pignatelli

Profile Information
Dr. Isabella Pignatelli
university of Lorraine
Assistant professor
GeoRessources Laboratory
"Cronstedtite polytypes in the Paris meteorite" Isabella Pignatelli, European Journal of Mineralogy Vol. 30 2018 349-354
The first detailed crystallo-chemical and crystallographic description of cronstedtite with extraterrestrial origin has been presented in this study. The analysed crystals have been found in the Paris meteorite, which is the least altered carbonaceous chondrite currently known, and they result from the pseudomorphism of anhydrous silicates. 3D electron diffraction data have been collected by electron diffraction tomography and used to identify the cronstedtite polytypes, because of their small size. All identified polytypes are MDO (Maximum degree of order), and the most abundant one is 1T. Many other crystals also belong to the Bailey's group (or OD subfamily) C, but their stacking disorder hampers the polytype identification. Only in one crystal, the 3T and 2M1 polytypes are recognised. TEM-EDX data indicate that the chemical composition of the crystals is similar, regardless their polytypic sequence.
"Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz" Isabella Pignatelli, Yann Le Pape, Kevin Field, Scientific Reports Vol. 6 2016 20155
Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar+-ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows little change in dissolution rate - although its density noted to reduce by ˜9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral’s atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. The outcomes have major implications on the durability of concrete structural elements formed with calcite or quartz bearing aggregates in nuclear power plants.