Georgia Cametti

New morphological, chemical, and structural data of woolly erionite-Na from Durkee, Oregon, U.S.A.

Abstract A detailed morphological, crystal-chemical, and structural characterization of erionite from the type locality of Durkee, Oregon, has been carried out by combining field emission scanning electron microscopy (FESEM) and laboratory parallel-beam transmission X‑ray powder diffraction (XRPD). According to the crystal-chemical formula (Na5.38K1.99Mg0.24)[Al7.66Si28.34O72.09]·29.83H2O, the sample has been classified as erionite-Na. The Rietveld refinement has indicated that the extraframework cations are located at three Ca1, Ca2, and Ca3 sites, the first one containing all available Mg. Moreover, the absence of the additional K2 site found in both dehydrated erionite and erionite-K has been demonstrated for this erionite sample. Furthermore, our results revealed the absence of Fe and Ca although previous investigations have reported the presence of a variable content of both these elements in erionite samples from Durkee. This is relevant information because it is well known from amphibole asbestos that Fe2+ has been claimed to be one of the causes of carcinogenesis by participating in Fenton chemistry and producing free radicals.

A Deep Look Into Erionite Fibres: an Electron Microscopy Investigation of their Self-Assembly.

The exposure of humans to erionite fibres of appropriate morphology and dimension has been unambiguously linked to the occurrence of Malignant Mesothelioma. For this reason, a detailed morpho-structural investigation through Electron Microscopy techniques has been performed on erionite samples collected at two different localities, Durkee (ED) and Rome (ER), Oregon, USA. The sample from Rome has been also investigated after a prolonged leaching with Gamble’s solution (ER4G) in order to evaluate the possible occurrence of morpho-structural modifications induced by this Simulated-Lung-Fluid (SLF). Here we report how the micrometric erionite fibres evolve in irregular ribbon- or rod-like bundles as a function of different nano-structural features. The reasons for the observed morphological variability have been explained by considering the structural defects located at ED surface fibrils (bi-dimensional ribbons) and the presence of nontronite, an iron-bearing clay mineral embedding the ER fibrils (mono-dimensional rods). ER4G shows a decrease in width of the rod-like fibres due to their partial digestion by SLF leaching, which synchronously dissolves nontronite. The reported results represent a valuable background toward the full comprehension of the morphological mechanisms responsible for potentially damage of lung tissue through the potential relocation of fibers to extrapulmonary sites, increasing the carcinogenic risk to humans.

Crystal chemical and structural modifications of erionite fibers leached with simulated lung fluids

Abstract Inhalation of erionite has been proven to be the cause of the extended epidemic of malignant mesothelioma occurring in Central Anatolia, Turkey, and of cases of lung diseases in the U.S.A. Its carcinogenicity is three orders of magnitude greater than that of regulated asbestos. Here we report the results of the investigation of the structural and crystal chemical modifications occurring in erionite leached with artificial lysosomal fluid (ALF) and Gamble’s solution. ALF leaching produces a migration of Na+ ions from Ca1 to Ca2 extraframework cationic site, without the occurrence of any significant modification of the chemical composition of the fibers. In contrast, leaching with Gamble’s solution induces a complex ionic-exchange process resulting in a temporary partial replacement of Na+ by Ca2+, coming from the fluid, which is fixed at a third Ca3 cationic site. Subsequently, the exchange process reverses. In fact, Ca2+ is removed from Ca3 and Na+ migrates back to Ca1, the structure being indistinguishable from the starting, unleached material. Such processes seem to be accompanied by a progressive amorphization of fibers. Present data could provide valuable background for a more detailed comprehension of the morphostructural/biological activity relationships inducing pathogenicity.