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Country rock identification and geology

The pre-existing rock into which an igneous intrusion is emplaced or through which a mineral vein or ore body is hosted. The country rock provides the structural and chemical environment that influences the form and composition of the intrusion or mineralization. Xenoliths of country rock are frequently found within intrusions, providing evidence of the surrounding lithology. Field: petrology. Example: Gold-bearing quartz veins in the Timmins district of Ontario are hosted in mafic volcanic country rock of the Abitibi greenstone belt, with mineralization concentrated along shear zones.. Related terms: Intrusion, Xenolith, Host rock, Wall rock.

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
2026-03-30T15:19:41.970235+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 Country rock mean in geology?
The pre-existing rock into which an igneous intrusion is emplaced or through which a mineral vein or ore body is hosted. The country rock provides the structural and chemical environment that influences the form and composition of the intrusion or mineralization. Xenoliths of country rock are frequently found within intrusions, providing evidence of the surrounding lithology.
What is an example of Country rock?
Gold-bearing quartz veins in the Timmins district of Ontario are hosted in mafic volcanic country rock of the Abitibi greenstone belt, with mineralization concentrated along shear zones.
Which earth-science field uses the term Country rock?
Country rock is used in petrology.
Which terms are related to Country rock?
Related terms in this reference are Intrusion, Xenolith, Host rock, Wall rock.

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