A Comprehensive Suite of d-θ Look-Up Tables for Indexing Zone-Axis SAED Patterns of Amphibole Asbestos and Related Minerals

The analysis of asbestos minerals below optical resolution is conducted by the analytical transmission electron microscopy (TEM). The Asbestos Hazard Emergency Response Act (AHERA) protocol mandates the measurement of three properties: the morphology by the TEM imaging, the elemental composition by the energy-dispersive X-ray spectroscopy (EDS), and the crystal structure by the zone-axis selected area electron diffraction (SAED). After the acquisition of a zone-axis SAED pattern with EDS-derived mineral identity, the practical and effective methodology of its indexing and interpretation is the comparison of the measured (observed) values of the d-spacings of two intersecting direct lattice planes and their interplanal angle against the reference values in pre-calculated d-spacing and interplanal angle look-up tables (d-θ table) based on the mineral’s unit cell parameters and symmetry. This paper presents a suite of hitherto most comprehensive d-θ look-up tables (more than 800 pages and 36,000 zone axes) for five regulated amphiboles (anthophyllite, grunerite, riebeckite, tremolite, and actinolite), three non-regulated ones (winchite, richterite, and cummingtonite), and talc, which could be confused with the regulated anthophyllite to facilitate the analysis of zone-axis SAED patterns. The procedure of using the d-θ look-up table is illustrated by two examples. Issues relevant to applications of d-θ table are also discussed.