xenocryst

geology

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July 15, 2026

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A xenocryst is a crystal that is foreign to the rock in which it occurs. This means it is a crystal that does not belong to the igneous body it is found within. Xenocrysts are distinct from autoliths, which are rock fragments genetically related to the igneous body itself.12

Xenoliths, which are rock fragments unrelated to the igneous body, are incorporated into magma while it is still fluid. These fragments can be altered by contact metamorphism, where heat and fluids change their mineralogy and chemistry. Studying these changes can provide insights into the temperature and composition of the magma.2

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igneous rock
Fabric
…phenocrysts are referred to as xenocrysts, while the aggregates can be termed xenoliths. The size of phenocrysts is essentially independent of their abundance relative to the groundmass, and they range in external form from euhedral to anhedral. Most of them are best described as subhedral. Because the groundmass constituents span…
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…phenocrysts are referred to as xenocrysts, while the aggregates can be termed xenoliths. The size of phenocrysts is essentially independent of their abundance relative to the groundmass, and they range in external form from euhedral to anhedral. Most of them are best described as subhedral. Because the groundmass constituents span…
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