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Mafic identification and geology

Describing igneous rocks and magmas rich in magnesium and iron, with silica content typically between 45–52%. Mafic rocks are dark-colored, dense, and composed primarily of olivine, pyroxene, and calcium-rich plagioclase feldspar. Common mafic rocks include basalt extrusive and gabbro intrusive . The term is a portmanteau of "magnesium" and "ferric" iron . Field: petrology. Example: The oceanic crust is composed almost entirely of mafic rock—basalt at the surface and gabbro below—with a total thickness of only 5–10 km, much thinner than the felsic continental crust.. Related terms: Felsic, Basalt, Gabbro, Ultramafic.

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
2026-03-30T15:19:42.055955+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 Mafic mean in geology?
Describing igneous rocks and magmas rich in magnesium and iron, with silica content typically between 45–52%. Mafic rocks are dark-colored, dense, and composed primarily of olivine, pyroxene, and calcium-rich plagioclase feldspar. Common mafic rocks include basalt extrusive and gabbro intrusive . The term is a portmanteau of "magnesium" and "ferric" iron .
What is an example of Mafic?
The oceanic crust is composed almost entirely of mafic rock—basalt at the surface and gabbro below—with a total thickness of only 5–10 km, much thinner than the felsic continental crust.
Which earth-science field uses the term Mafic?
Mafic is used in petrology.
Which terms are related to Mafic?
Related terms in this reference are Felsic, Basalt, Gabbro, Ultramafic.

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