STABILITY RELATIONS OF POLYMORPHS OF ALUMINUM SILICATE - SURVEY AND SOME COMMENTS

Existing determinations of pressure-temperature relations of sillimanite, kyanite, and andalusite show large discrepancies in locations both of univariant lines and of invariant point; discrepancies probably resulted partly from determination of synthesis rather than stability fields and partly from experimental difficulties in pressure determinations; however, these explanations probably do not account for all observed spread, and possible effects of compositional variations cannot be excluded.