Analysis of Vermiculite for Asbestos and Screening for Vermiculite from Libby, Montana

2015:174:Millette

Microscope, Vol 63:2 p.59-75

Millette, Compton

Abstract:

There is general agreement that a negative finding using the usual bulk microscope analysis for building materials without any pre-treatment of the vermiculite is not reliable. Preparation procedures involving sedimentation, grinding and total matrix reduction with acid/base dissolution have been used to improve the ability to find asbestos if present in vermiculite ores and products. This article contains information on most of the available methods for vermiculate analysis based on the extensive review of published articles, government reports and other documents. The limited data in the published articles concerning the major vermiculite sources in the Enoree district in South Carolina; Louisa County, Virginia; Palabora, South Africa; and Xinjiang Province in China strongly suggest that commercially available non-Libby vermiculite is not contaminated with affable asbestos to the extent that the vermiculite from Libby, Montana. Differentiating Libby vermiculite insulation from other commercial sources can be done reliably and inexpensively with a routine chemical barium test as long as the insulation sample is not a mixture of Libby vermiculite and other materials. A qualitative transmission electron microscopy (TEM) analysis of a filtration of the fibers suspended in water from a sample of a vermiculite attic insulation (VAI) that was prepared using the sedimentation procedure appears to be a reliable method of confirming Libby vermiculite.

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