The number of tetrahedra in the crystal structure and how they are arranged determine how a silicate mineral is classified. Serpentine silicates are classified as ‘sheet silicates’ because the tetrahedra are arranged to form sheets. Amphibole silicates are classified as ‘chain silicates’ because the tetrahedra are arranged to form a double chain of two rows aligned side by side. Magnesium is coordinated with the oxygen atom in serpentine silicates. In amphibole silicates, cationic elements such as aluminium, calcium, iron, magnesium, potassium, and sodium are attached to the tetrahedra. Amphiboles are distinguished from one another by their chemical composition. The chemical formulas of asbestos minerals are idealized. In natural samples, the composition varies with respect to major and trace elements. More detailed information on the
chemical and physical characteristics of asbestos – including atomic structure, crystal polytypes, fibre structure, chemistry and impurities – can be found in the previous IARC Monograph