The behaviour of vitreous silica under sudden changes of temperature is most remarkable.
The rate of expansion of vitreous silica has been studied by H. le Chatelier, and more recently by Callendar.
The melting point of vitreous silica cannot be definitely stated.
The skeleton is formed by small crystals and long threads of vitreous silica, cemented together, during life, by protoplasm.
The density of vitreous silica is very near to that of ordinary amorphous silica.
vitreous silica is less hard than chalcedony, but harder than felspar.