Tridymite stability range

The first detailed data on the inversions of S1O2 were published in the classical studies by Fenner (1913, 1914) who used sodium tungstate as the mineralizer. As proved later, the use of the mineralizer affected the conclusions which had assumed tridymite to be a stable phase with a precisely defined stability region. The stability ranges of the Si02 phases, according to Fenner, are represented in the schematic equilibrium diagram in Fig. 4. 

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