Asbestos is a generic term given to several naturally-occurring silicate minerals.
Chrysotile is the form most widely found, and is the least harmful. Crocidolite, on the other hand, is the most harmful, and its use was banned in the 1970s. The use of asbestos declined steadily from the 1960s and only Chrysotile can now be used. However it is likely that its use will also be banned in the near future. Although numerous buildings have been stripped of asbestos and safer materials used as replacements, most of the asbestos ever used is still in place, and often its existence remains undetected.