Department of Geology

THE HABIT OF ASBESTIFORM AMPHIBOLES: IMPLICATIONS FOR THE ANALYSIS OF BULK SAMPLES


REFERENCE: Wylie, A. G., "The Habit of Asbestiform Amphiboles: Implications for the Analysis of Bulk Samples",  Advances in Environmental Measurement Methods for Asbestos, ASTM STP 1342, M.E. Beard, H. L. Rooks, Eds., American Society for Testing and Materials, West Conshohocken, PA, 1999.

ABSTRACT: Evidence on the carcinogenicity of fibrous minerals supports the conclusion that amphiboles must form in an asbestiform habit in order to pose a risk to human health.  Furthermore, the asbestiform habit controls many of the physical properties of asbestos. Because of the distinctive characteristics of the asbestiform habit, populations of asbestiform amphiboles can be distinguished from populations of amphibole cleavage fragments by light microscopy.  Populations of asbestos fibers longer than 5 ?m are characterized by fibers that occur in bundles, are often curved, and have very high aspect ratios (mean aspect ratio > 20:1 - 100:1) and narrow widths, usually less than 0.5 ?m.  It is inappropriate to apply a 3:1 aspect ratio criterion to identify amphibole asbestos. Other minerals that crystallize in a habit similar to asbestos do not necessarily pose the same risk because factors such as friability, biodurability, bioavailability and surface chemistry are important in determining carcinogenicity of mineral fibers.

KEY WORDS: asbestos, asbestiform, amphibole, mineralogical characteristics