igneous
Basalt Pebble
Basalt (Mafic Extrusive Igneous Rock)
AI-generated identification · may be incorrectHardness around 6 on Mohs scale. Color ranges from dark gray to black with a dull, earthy to sub-metallic luster. Fine-grained (aphanitic) texture, composed mainly of plagioclase feldspar and pyroxene.
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Physical properties
Hardness around 6 on Mohs scale. Color ranges from dark gray to black with a dull, earthy to sub-metallic luster. Fine-grained (aphanitic) texture, composed mainly of plagioclase feldspar and pyroxene.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of Earth or terrestrial planets. The smooth, rounded shape indicates natural water erosion from riverbeds or coastal environments.
Uses & applications
Used widely in construction as crushed stone, aggregate in concrete, road base, asphalt paving, and as decorative river rock in landscaping.
Geological facts
Basalt is the most common rock type in Earth's crust, making up almost all oceanic crust as well as large volcanic provinces like the Columbia River Basalt Group. It is also extremely common on the Moon and Mars.
Field identification & locations
Identified in the field by its dense weight, fine-grained texture, dark color, and lack of visible large quartz crystals. Commonly found along stream beds, beaches, and volcanic landscapes.
