Preliminary research has been carried out on the thermal modification of chrysotile asbestos. Destruction of the tubular structure of asbestos was achieved by calcination at 1000°C. In order to characterize the changes accompanying thermal modification both natural asbestos and calcined asbestos were subjected to thermogravimetric and differential thermal analysis, X-ray analysis and examination by scanning electron microscopy. The possibility of utilization of the calcined asbestos in the presence of a phosphate binder for the manufacture of refractory materials has been demonstrated.