POLYMORPHISM OF SILICA

A study of the stability relations of pure silica phases is described. It is shown that although cristobalite can be produced from pure quar tz by heating it is not possible to produce tridymite in this fashion; a flux or mineralizer is required for tridymite formation and even in this case cristobalite is produced before any tridymite is observed. Thus it is concluded that the stability relations for the silica miner als proposed by Fenner are incorrect and that tridymite is not a stabl e phase in the pure silica system.