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Xenocryst identification and geology

A single crystal found in an igneous rock that is foreign to the magma in which it occurs, having been incorporated from the country rock or from an earlier, unrelated magmatic episode. Xenocrysts are distinguished from phenocrysts which crystallized from the host magma by their disequilibrium textures—reaction rims, embayments, and compositional mismatch with the surrounding rock. Field: petrology. Example: Quartz xenocrysts found in basaltic lava from the Eifel volcanic field in Germany show reaction rims of pyroxene, indicating they were scavenged from granitic country rock and are unstable in the basaltic melt.. Related terms: Xenolith, Phenocryst, Contamination, Assimilation.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.127987+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Xenocryst mean in geology?
A single crystal found in an igneous rock that is foreign to the magma in which it occurs, having been incorporated from the country rock or from an earlier, unrelated magmatic episode. Xenocrysts are distinguished from phenocrysts which crystallized from the host magma by their disequilibrium textures—reaction rims, embayments, and compositional mismatch with the surrounding rock.
What is an example of Xenocryst?
Quartz xenocrysts found in basaltic lava from the Eifel volcanic field in Germany show reaction rims of pyroxene, indicating they were scavenged from granitic country rock and are unstable in the basaltic melt.
Which earth-science field uses the term Xenocryst?
Xenocryst is used in petrology.
Which terms are related to Xenocryst?
Related terms in this reference are Xenolith, Phenocryst, Contamination, Assimilation.

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