Zeolites belonging to erionite and offretite families were recently discovered to be very dangerous for the human health since demonstrated to be carcinogenic (e.g. Carbone et al., 2007; Dogan et al., 2008). Notwithstanding this, the morphologies of erionite and offretite fibers have not yet been fully understood and many mineralogical and toxicological aspects are still unknown. Moreover, it is unclear whether the mineralogical similarity between erionite and offretite has any health implications. For these reasons, it is of paramount importance to improve the knowledge of their physical and chemical properties because they may be related to the carcinogenic potential of these fibrous zeolites. Identification of (and distinction between) erionite and offretite can be difficult because of (i) their mineralogical similarities and (ii) the possibility of intergrowth of the two species within each crystal (Passaglia et al., 1998). Here we present morphological and chemical data of erionite and offretite samples, collected from various localities. Four main morphological types of crystals have been observed. (I) Elongated prisms, often grouped in sub-spherical forms, with a strong tendency to develop thin fibers. (II) Very elongated, fibrous prisms, terminated by a wider, massive form with pseudo-hexagonal section. (III) Stocky prismatic forms, with a strong tendency to generate fibers at the ends of the crystals. (IV) Extremely fibrous crystals with "soft" appearance, which can be found both as single-phases and in epitaxial growth with other minerals. Chemical data indicate the presence of a wide range of compositions, based on extra-framework dominant cation. Types I and III can be referred to both offretite and erionite compositions; this latter has been found as K-, Na- and Caerionite. Type II shows a notably chemical variation: the prismatic, fibrous body corresponds to Na-erionite, while the wider, massive termination is offretite. Type IV is always erionite (both K- and Ca-members) and no offretite samples have been found with this extremely fibrous habit. Intermediate chemical compositions could be natural or due to intimate intergrowths of these two minerals. A better understanding of the potential toxicity is needed across the range of erionite and offretite compositions.

Morphology and chemistry of erionite and offretite: increasing data of carcinogenic fibrous zeolites

GIORDANI, MATTEO;MATTIOLI, MICHELE
2015-01-01

Abstract

Zeolites belonging to erionite and offretite families were recently discovered to be very dangerous for the human health since demonstrated to be carcinogenic (e.g. Carbone et al., 2007; Dogan et al., 2008). Notwithstanding this, the morphologies of erionite and offretite fibers have not yet been fully understood and many mineralogical and toxicological aspects are still unknown. Moreover, it is unclear whether the mineralogical similarity between erionite and offretite has any health implications. For these reasons, it is of paramount importance to improve the knowledge of their physical and chemical properties because they may be related to the carcinogenic potential of these fibrous zeolites. Identification of (and distinction between) erionite and offretite can be difficult because of (i) their mineralogical similarities and (ii) the possibility of intergrowth of the two species within each crystal (Passaglia et al., 1998). Here we present morphological and chemical data of erionite and offretite samples, collected from various localities. Four main morphological types of crystals have been observed. (I) Elongated prisms, often grouped in sub-spherical forms, with a strong tendency to develop thin fibers. (II) Very elongated, fibrous prisms, terminated by a wider, massive form with pseudo-hexagonal section. (III) Stocky prismatic forms, with a strong tendency to generate fibers at the ends of the crystals. (IV) Extremely fibrous crystals with "soft" appearance, which can be found both as single-phases and in epitaxial growth with other minerals. Chemical data indicate the presence of a wide range of compositions, based on extra-framework dominant cation. Types I and III can be referred to both offretite and erionite compositions; this latter has been found as K-, Na- and Caerionite. Type II shows a notably chemical variation: the prismatic, fibrous body corresponds to Na-erionite, while the wider, massive termination is offretite. Type IV is always erionite (both K- and Ca-members) and no offretite samples have been found with this extremely fibrous habit. Intermediate chemical compositions could be natural or due to intimate intergrowths of these two minerals. A better understanding of the potential toxicity is needed across the range of erionite and offretite compositions.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11576/2641635
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