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Ultramafic identification and geology

Describing igneous rocks and magmas with very low silica content <45% and very high magnesium and iron content, composed predominantly of olivine and pyroxene with little or no feldspar. Ultramafic rocks include peridotite, dunite, and pyroxenite. They are the dominant rock type of the Earth's upper mantle and occur at the surface in ophiolite complexes, kimberlite pipes, and layered intrusions. Field: petrology. Example: The ultramafic rocks of the Bay of Islands ophiolite complex in Newfoundland represent a slice of oceanic mantle thrust onto the continental margin during the Ordovician, now weathering to produce distinctive serpentinite barrens with sparse, unique vegetation.. Related terms: Mafic, Peridotite, Olivine, Mantle.

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
2026-03-30T15:19:42.096023+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 Ultramafic mean in geology?
Describing igneous rocks and magmas with very low silica content <45% and very high magnesium and iron content, composed predominantly of olivine and pyroxene with little or no feldspar. Ultramafic rocks include peridotite, dunite, and pyroxenite. They are the dominant rock type of the Earth's upper mantle and occur at the surface in ophiolite complexes, kimberlite pipes, and layered intrusions.
What is an example of Ultramafic?
The ultramafic rocks of the Bay of Islands ophiolite complex in Newfoundland represent a slice of oceanic mantle thrust onto the continental margin during the Ordovician, now weathering to produce distinctive serpentinite barrens with sparse, unique vegetation.
Which earth-science field uses the term Ultramafic?
Ultramafic is used in petrology.
Which terms are related to Ultramafic?
Related terms in this reference are Mafic, Peridotite, Olivine, Mantle.

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