igneous
Likely basalt (possibly vesicular basalt)
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine, with iron-titanium oxides
AI-generated identification · may be incorrectDark gray to black, fine-grained, typically dull to weakly vitreous; hardness about 5–6 Mohs, no prominent cleavage, and specific gravity around 2.8–3.0. The specimen appears weathered and partly coated with pale secondary minerals, making identification from the image uncertain.
Identified More igneous →
Explore Likely basalt (possibly vesicular basalt) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained, typically dull to weakly vitreous; hardness about 5–6 Mohs, no prominent cleavage, and specific gravity around 2.8–3.0. The specimen appears weathered and partly coated with pale secondary minerals, making identification from the image uncertain.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface, commonly in volcanic flows, oceanic crust, and hotspot environments. Individual pieces may range from geologically young lava to ancient basalt of any age.
Uses & applications
Widely used as crushed aggregate, road base, railway ballast, building stone, and occasionally decorative material; generally not used as a gemstone.
Geological facts
Basalt is the most abundant volcanic rock and forms much of the ocean floor. Vesicles, if present, record gas bubbles trapped during lava cooling; pale patches may represent weathering or zeolite/calcite alteration.
Field identification & locations
Identify by its black fine-grained texture, substantial weight, and lack of visible large crystals; a streak, hardness, and acid test can help distinguish it from slag or dark metamorphic rocks. Common worldwide, especially volcanic regions and oceanic islands.
