A fine-grained extrusive igneous rock that forms from the rapid cooling of lava. It is the most common rock type on Earth's surface, forming most ocean floors and volcanic islands. Texture: Aphanitic fine-grained. Rock type: Igneous Extrusive. Grain size: Fine. Minerals present: Plagioclase, Pyroxene, Olivine, Magnetite. Formation: Forms from rapid cooling of mafic iron and magnesium-rich lava at or near the Earth's surface. Common geological settings: Found at mid-ocean ridges, volcanic islands Hawaii, Iceland , and in large igneous provinces. Forms lava flows and pillows. Common look-alikes and related entries: Gabbro, Andesite, Diabase.
Previous: Banded Iron Formation — Distinctive Precambrian sedimentary rock with alternating layers of iron-rich hematite/magnetite and silica-rich chert bands.
Next: Basanite — Olivine-bearing alkaline volcanic rock similar to tephrite but with significant olivine. Rich in feldspathoids.
Vesicular rocks — Place this specimen in a broader field-identification workflow.
Glassy rocks — Place this specimen in a broader field-identification workflow.
Porphyritic rocks — Place this specimen in a broader field-identification workflow.
Basalt vs Andesite — Compare observable properties and safer field tests.
Obsidian vs Basalt — Compare observable properties and safer field tests.
Granite vs Basalt — Compare observable properties and safer field tests.
Basalt vs Gabbro — Compare observable properties and safer field tests.
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.
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Last updated
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Rocks — U.S. National Park Service. Authoritative overview of rock groups, the rock cycle, and geologic processes.
A fine-grained extrusive igneous rock that forms from the rapid cooling of lava. It is the most common rock type on Earth's surface, forming most ocean floors and volcanic islands.
How can you identify Basalt?
Compare several properties rather than relying on colour alone. This entry records rock type: Igneous Extrusive; texture: Aphanitic fine-grained; grain size: Fine; common minerals: Plagioclase, Pyroxene, Olivine, Magnetite. Confirm an important identification with additional field tests or qualified laboratory work.
How does Basalt form?
Forms from rapid cooling of mafic iron and magnesium-rich lava at or near the Earth's surface.
Where is Basalt commonly found?
Found at mid-ocean ridges, volcanic islands Hawaii, Iceland , and in large igneous provinces. Forms lava flows and pillows.
What is Basalt commonly confused with?
Basalt may be confused with Gabbro, Andesite, Diabase. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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