xenocryst

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xenocryst A crystal in an igneous rock which has not crystallized from the melt but has been introduced into the melt from an external source, e.g. the surrounding country rocks or a previously crystallized part of the same igneous body. Xenocrysts, which are usually in disequilibrium with the melt, contrast with phenocrysts which have crystallized in equilibrium from the melt.

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xenocryst

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