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Igneous identification and geology

Describing rocks formed by the solidification of magma or lava. Igneous rocks are classified as intrusive plutonic if they crystallized below the surface, or extrusive volcanic if they solidified at the surface. They are further classified by chemical composition felsic, intermediate, mafic, ultramafic and texture phaneritic, aphanitic, porphyritic, glassy, pyroclastic . Field: petrology. Example: The Earth's oceanic crust is composed entirely of igneous rocks—basaltic pillow lavas at the surface, sheeted diabase dikes below, and gabbro at the base—formed at mid-ocean ridges.. Related terms: Magma, Intrusive, Extrusive, Crystallization.

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
2026-03-30T15:19:42.027557+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 Igneous mean in geology?
Describing rocks formed by the solidification of magma or lava. Igneous rocks are classified as intrusive plutonic if they crystallized below the surface, or extrusive volcanic if they solidified at the surface. They are further classified by chemical composition felsic, intermediate, mafic, ultramafic and texture phaneritic, aphanitic, porphyritic, glassy, pyroclastic .
What is an example of Igneous?
The Earth's oceanic crust is composed entirely of igneous rocks—basaltic pillow lavas at the surface, sheeted diabase dikes below, and gabbro at the base—formed at mid-ocean ridges.
Which earth-science field uses the term Igneous?
Igneous is used in petrology.
Which terms are related to Igneous?
Related terms in this reference are Magma, Intrusive, Extrusive, Crystallization.

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