Asbestos Identification

Crocidolite (blue) - Amosite (brown) - Chrysotile (white)

Introduction

The three principal forms of asbestos found in bulk materials are Crocidolite (blue), Amosite (brown) and Chrysotile (White). Chrysotile is the form most commonly encountered.

The other regulated forms of asbestos are fibrous actinolite, tremolite and Anthophyllite. These were used to a lesser extent and sometimes can be found in bulk materials as trace contaminants.

In more recent years, its hazardous nature became apparent. The size and shape of the fibres allow them to be easily inhaled, penetrating the airways and lungs. Exposure to asbestos fibres can give rise to lung cancer, asbestosis and mesothelioma

Identification

Fortunately the various forms of asbestos exhibit distinctive optical properties, most notably the refractive index. Being crystalline materials, each form has more than one refractive index, depending on the direction from which it is observed

The method for asbestos identification is set down in the HSEs MDHS 77

The material is first examined under a stereo microscope to assess the morphology and physical properties of the fibre.

The fibre bundle is then mounted on a slide in an appropriate refractive index liquid. It is identified as one of the six regulated asbestos types according to its optical properties using polarised light microscopy.

The following properties of the fibre are assessed using PLM, normally in this order:

Morphology

Colour & Pleochroism

Birefringence

Angle of Extinction

Sign of Elongation

Dispersion staining colours

The unique dispersion staining colours for the fibres are quite beautiful and can be observed under the microscope when the fibres are in their matching RI liquid.

Voelcker Consultants has carried out numerous surveys of houses, flats, offices, factories, public buildings and ships over the years, in accordance with MDHS100. Please contact us if you would like to discuss a project or for some advice. Initial consultations are free of charge.

For more information see our Asbestos Section on our web site, or contact us at CL Voelcker