igneous
Basalt with Amygdules
Extrusive Igneous Rock (Mafic)
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale; dark gray to black color; fine-grained aphanitic groundmass with lighter-colored secondary mineral infillings (amygdules such as calcite, quartz, or zeolites); dull to sub-vitreous luster.
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Physical properties
Hardness of 6 on the Mohs scale; dark gray to black color; fine-grained aphanitic groundmass with lighter-colored secondary mineral infillings (amygdules such as calcite, quartz, or zeolites); dull to sub-vitreous luster.
Formation & geological history
Formed from the rapid cooling of low-viscosity, iron- and magnesium-rich lava flows at the Earth's surface. Gas bubbles trapped during cooling later fill with mineral-rich hydrothermal fluids to form amygdules.
Uses & applications
Used in construction, road aggregate, railroad ballast, and occasionally cut and polished as decorative stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Easily identified by its dark, fine-grained matrix containing distinctive rounded or oval vesicles filled with secondary white or light-colored minerals; common in volcanic regions worldwide.
