igneous
Fine-grained dark igneous rock, likely basalt
Basalt; predominantly plagioclase feldspar and pyroxene, commonly with minor olivine and iron-titanium oxides
AI-generated identification · may be incorrectTypically dark gray to black, dull to subtly granular, with interlocking crystals too small to see clearly; hardness about 6, no obvious cleavage, and specific gravity roughly 2.8–3.0. The specimen appears dense and fine-grained, though its weathered surface makes exact identification uncertain.
Identified More igneous →
Explore Fine-grained dark igneous rock, likely basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically dark gray to black, dull to subtly granular, with interlocking crystals too small to see clearly; hardness about 6, no obvious cleavage, and specific gravity roughly 2.8–3.0. The specimen appears dense and fine-grained, though its weathered surface makes exact identification uncertain.
Formation & geological history
Basalt forms when low-viscosity mafic lava cools rapidly at or near Earth’s surface, commonly in volcanic flows, oceanic crust, and flood-basalt provinces. It can range from recent eruptions to rocks billions of years old.
Uses & applications
Used extensively as crushed aggregate, road base, railroad ballast, concrete material, riprap, and dimension stone; attractive varieties are used decoratively but rarely as jewelry.
Geological facts
Basalt is the most abundant volcanic rock and makes up much of the ocean floor. Vesicles, visible olivine crystals, or a glassy groundmass may indicate related basaltic varieties.
Field identification & locations
Identify it by its dark color, fine interlocking texture, substantial weight, and lack of visible layering; distinguish it from darker granite by its much finer grain. Common worldwide, especially volcanic regions and oceanic terrains.
