Analysis of amphibole asbestos in chrysotile and other minerals

Chrysotile asbestos and many other mineral raw materials contain amphibole minerals which may be asbestiform. There is currently no analytical method which will detect the presence of amphibole at sufficiently low limits to preclude the possibility of inadvertent exposure of persons handling these materials to hazardous airborne fibre concentrations. A method of chemical digestion of chrysotiles has been tested with regard to the determination of their tremolite contaminant content and this has been applied to a range of chrysotile and other minerals. The method improves the sensitivity of the amphibole analysis at least 10-fold giving detection limits of 0.01-0.05% in chrysotile by X-ray diffractometry (XRD). The difficulties arising from compositional and morphological variations are discussed in the context of the potential hazards from airborne fibres and the relative values of analyses by XRD, infrared spectrophotometry (IR) and electron microscopy. It is concluded that XRD and IR are useful as screening methods for the detection of amphibole in chrysotile but other materials should be analysed by optical or electron microscopy.