The polymorphism of enstatite has been studied undel various heating and cooling rates using high temperature single-crystal X-ray techniques. Rapid quenches of protoenstatite produce twinned low clinoenstatite, while slower cooling rates produce mixtures of Ċlinoenstatite and up to fifty percento rthoenstatite.L arge strain energiesa ppeart o account for the martensitic nature of coherent transformations between enstatite polymorphs and the observation that different quench rates produce differing products. A modification of the transformation model of Sadanaga, Okamura, and Takeda (1969) and Coe (1970) better accounts for the observed nature of the transformations. No evidence of a stability field for high clinoenstatite above that of protoenstatite was observed when a crystal of protoenstatite underwent partial, incongruent melting to forsterite plus liquid.

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