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Gabbro identification and geology

Gabbro rock reference specimen

Dark, coarse-grained intrusive rock rich in pyroxene and calcium plagioclase. The plutonic equivalent of basalt. Texture: Phaneritic. Rock type: Igneous Intrusive. Grain size: Coarse. Minerals present: Plagioclase Ca-rich, Augite, Olivine, Hornblende. Formation: Crystallizes slowly from mafic magma deep in the crust, often in layered intrusions and at mid-ocean ridges. Common geological settings: Bushveld Complex South Africa , Stillwater Montana , oceanic crust layer 3. Common look-alikes and related entries: Diorite, Basalt, Diabase.

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
2026-03-30T14:38:06.011512+00:00
Review status
Published; not independently peer-reviewed
  • Rocks — U.S. National Park Service. Authoritative overview of rock groups, the rock cycle, and geologic processes.
  • Can you identify my rock or mineral? — U.S. Geological Survey. Identification limitations and routes to in-person professional verification.

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Common questions

What is Gabbro?
Dark, coarse-grained intrusive rock rich in pyroxene and calcium plagioclase. The plutonic equivalent of basalt.
How can you identify Gabbro?
Compare several properties rather than relying on colour alone. This entry records rock type: Igneous Intrusive; texture: Phaneritic; grain size: Coarse; common minerals: Plagioclase Ca-rich, Augite, Olivine, Hornblende. Confirm an important identification with additional field tests or qualified laboratory work.
How does Gabbro form?
Crystallizes slowly from mafic magma deep in the crust, often in layered intrusions and at mid-ocean ridges.
Where is Gabbro commonly found?
Bushveld Complex South Africa , Stillwater Montana , oceanic crust layer 3.
What is Gabbro commonly confused with?
Gabbro may be confused with Diorite, Basalt, Diabase. Compare multiple diagnostic properties because colour and surface appearance can overlap.

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