Asbestos fibres, coloured scanning electron micrograph (SEM). Asbestos is a fibrous naturally- occurring mineral. This is a type of asbestos that is called crysotile. The fibres are very resistant to heat and chemicals and so can be used to make fire-proof fabrics, brake linings and electrical and heating insulation. It is also used to make a lightweight cement. Unlike older types of asbestos that contained amphibole fibres and were crumbly (friable) and dusty, crysotile products are dense and safe if used properly. Asbestos is very toxic when inhaled as dust particles. Prolonged exposure causes a fatal lung disease known as asbestosis. Magnification: x510 at 6x7cm size.