igneous
Likely basalt fragment
Basalt; predominantly plagioclase feldspar and pyroxene, commonly with olivine
AI-generated identification · may be incorrectDark gray to black, fine-grained, generally dull to weakly vitreous; hardness about 5–6 Mohs, massive texture, with no obvious cleavage visible. The image is low-resolution, so identification is provisional.
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Physical properties
Dark gray to black, fine-grained, generally dull to weakly vitreous; hardness about 5–6 Mohs, massive texture, with no obvious cleavage visible. The image is low-resolution, so identification is provisional.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, commonly in oceanic crust, volcanic fields, and flood-basalt provinces. It may range from recent volcanic material to rocks billions of years old.
Uses & applications
Used extensively as crushed aggregate, road base, railway ballast, riprap, and building stone; attractive polished pieces may be used decoratively. This small irregular fragment has negligible commercial value.
Geological facts
Basalt is Earth’s most abundant volcanic rock and commonly forms pillow lavas beneath oceans. Vesicles, olivine grains, or a visible fine crystalline texture would strengthen the identification.
Field identification & locations
Look for a dense black-to-gray, fine-grained rock that is heavier than similarly sized felsic rocks and lacks visible large crystals; a streak, magnet test, and fresh broken surface help. Common worldwide, especially volcanic regions and oceanic crust.
