THE ASBESTOS FAMILY OF FIBRES

Asbestos is a collective term given to 6 naturally occurring minerals that are incombustible and separable into filaments: chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite. Only the first three have wide-spread commercial use. Chrysotile is a member of the serpentine group of minerals; crocidolite, amosite and the others belong to the amphibole group. Chrysotile, or white asbestos, currently accounts for more than 99% of world asbestos consumption. Its fibres are characterized by high tensile strength, resistance to alkalies, high flexibility and good spinnability.

Different physical and chemical properties

Chrysotile asbestos differs considerably from amphibole varieties in both physical and chemical composition. Visually, white chrysotile fibres are softer and silkier than amphiboles, which are stiffer and needle-like. Most notable is the relatively high iron content of amphibole varieties compared to chrysotile. These and other differences appear to explain the greater durability or biopersistance of amphiboles in living tissue, and thus their higher fibrogenic and carcinogenic potential. The relative toxicity of chrysotile and amphiboles is reviewed in greater detail in Module 3.

CHRYSOTILE

AMOSITE

CROCIDOLITE