Width Distributions of Asbestos and Non-Asbestos Amphibole Minerals

Amphibole asbestos fibers and non-asbestos amphibole particles have been shown to have different size characteristics, in addition to their morphological differences. There is a tendency, however, among laboratories and some regulators to ignore the morphological differences and to simply rely on a minimal aspect ratio to determine whether a particle is an asbestos fiber. This study, part of a larger evaluation of amphibole minerals, was undertaken to provide supporting size data that can be used to identify populations of asbestos and non-asbestos amphibole minerals. The asbestos samples average 0.27 μm in width with 90% thinner than 0.5 μm. In contrast, the non-asbestos amphiboles average 0.97 μm wide with 75% wider than 0.53 μm. The average aspect ratios were 76 : 1 for asbestos and 16 : 1 for the non-asbestos samples. These data confirm the historical distinctions of asbestos and non-asbestos amphibole minerals.