Analytical Approach for Identification of the Zeolite Erionite
THE MICROSCOPE
2015, Volume 63:4, pp. 161–171
DOI
https://doi.org/10.59082/RCMW2972
AUTHORS
Kristina P. Pourtabib and Mickey E. Gunter
ABSTRACT
The need for precise identification of the fibrous/acicular zeolite mineral erionite has become increasingly important due to erionite’s ties to mesothelioma in Turkey and to lung disease in western North America (1). The regulatory community struggles to unambiguously identify asbestiform minerals when they occur in natural rather than built environments. Zeolites present an even more unique set of problems due to the similar cation content and crystal structure observed between different zeolite species such as erionite and offretite. Currently, there is a lack of regulatory methods for accurately identifying erionite particles in nature. We tested a variety of techniques that can be applied for the identification of erionite, including the use of selected area electron diffraction (SAED) with transmission electron microscopy (TEM), indirect zeolite identification with polarized light microscopy (PLM), and powder X-ray diffraction (XRD) for analysis of bulk composition. We found that smaller TEM-scale data provides paramount structural information in the form of diffraction patterns because erionite shows systematic absences (i.e., diffraction constraints) along uv0 of 00l = 2n due to its space group symmetry, while the other zeolites in this study will show different diffraction constraints along c*, and different repeats in c (2). We have shown that by using a combination of scale-dependent identification methods, such as TEM, PLM and XRD, these zeolites can be accurately distinguished from one another with sufficient care.