A review of the range of fibrous amphibole crystal morphologies between asbestiform fibers and cleavage fragments as revealed by TEM/SEM studies and how their interpretation impacts analytical testing results used in asbestos exposure studies.

A review of a range of TEM and SEM studies of fibrous amphiboles has been undertaken. Of particular relevance, are TEM studies where fibers were viewed down the fiber axis which identified the following common features to a greater or lesser degree: 1) crystal structure defects & stacking faults, 2) the presence of fiber cross-sectional edges which are rounded, irregular, faceted, or hybrid, and 3) intergrowths with other crystalline phases. Also of relevance are SEM studies where external fiber morphology can be studied in detail. The features identified in these studies have been used by various parties to either include or exclude identified fibers as asbestos. This review contrasts and compares the fiber images presented in the TEM/SEM studies and attempts to summarize the issues and arguments being made by various parties, including mineralogists, regulators, litigators in asbestos injury lawsuits, and others, in the debate as to whether fibrous amphiboles are, or are not, asbestos and to be included during analytical testing.