Tremolite asbestos in the laboratory (C) Daniel Friedman Definition & Chemical Composition of Asbestos
Definition & chemical composition of types of asbestos

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What is asbestos?

This article gives a definition of asbestos and interestingly, explains that the name asbestos does not refer to a distinct mineral species but it is a commercial term applied to fibrous varities of several minerals differing widely in composition, strength, flexibility, and usefulness.

This article series describes the physical properties of asbestos including its mechanical, chemical, electrical and related properties both in pure asbestos form and when asbestos is mixed with other materials. Page top photo: tremolite asbestos fibers in the microscopy laboratory - ©Daniel Friedman

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Definition of Asbestos Fibers

Asbestos ore showing parallel fiber structure - Rosato (C) InspectApediaAsbestos is the name given to a number of mineral silicates. The name asbestos does not refer to a distinct mineral species but it is a commercial term applied to fibrous varities of several minerals differing widely in composition, strength, flexibility, and usefulness.

Figure 2.2. View showing parallel fiber structure of asbestos vein, (Courtesy Johns-Manville-Corp.) [Click to enlarge any image]

Chemical and mineralogical studies show that asbestos is of mineral origin. The most important variety is chrysotile, which constitutes approximately 95 per cent of total world prOduction. Its wide use is caused by the fact that its fibers are generally strong, flexible, chemical resistant, and heat resistant.

Other varieties of asbestos are crocidolite, amosite, anthophyllite, tremolite, and actinolite; each has its own field of utility. The chrysotile is classified as being of the serpentine family. The others are of the amphibole family.

The amphibole groups of asbestos minerals were originally known as hornblende, inasmuch as they were closely related to the minerals tremolite and actinolite. This group is made up of complex silicates. Such varied types of fibers as tremolite and actinolite have widely different chemical structures. Sometimes, it is difficult to identify these different minerals except by x-ray. The amphibole group is interesting insofar as chemical aspects are concerned;, although, weak fibrous structures are present in the group..

Specific gravity of asbestos fibers ranges from 2.5 for chrysotile to 3.3 for the other types.

Chemical Compostion of Chrysotile, Crocidolite, Amnosite, Anthophyllite & Tremolite Asbestos

The chemical composition of the various types of asbestos are shown in Table 2.1.

TABLE 2.1. CHEMICAL COMPOSITION OF VARIOUS TYPES OF ASBESTOS * [ Click to enlarge or view details]

Chemical composition of types of asbestos - Rosato

* Encyclopedia of Chemical Technology, Vol. 2, New York and London, Intérscience Publisher (1948).

The chemical feature common to all asbestos is that they are hydrated silicates The degree of hydration varies from approximately one per cent in some types to as much as approximately 14 per cent in most kinds of chiysotile It generally accepted that asbestos is a metamorphic product derived from certain types of silica-bearing minerals.

Asbestos is generally as dense as the rock in which it occurs but it forms masses of fibers

Additional distinctions among the various types of asbestos are given at ASBESTOS TYPES.



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