igneous
Amygdaloidal Basalt
Mafic extrusive igneous rock with secondary mineral infillings
AI-generated identification · may be incorrectHardness 5-6 on Mohs scale, grayish-purple matrix with pale green or white secondary mineral vesicles, dull to sub-vitreous luster, fine-grained aphanitic texture.
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Physical properties
Hardness 5-6 on Mohs scale, grayish-purple matrix with pale green or white secondary mineral vesicles, dull to sub-vitreous luster, fine-grained aphanitic texture.
Formation & geological history
Formed by volcanic cooling of basaltic lava where gas bubbles create cavities later filled by mineral-rich hydrothermal fluids.
Uses & applications
Used primarily in aggregate, landscaping, road construction, and educational geology collections.
Geological facts
Vesicles in basalt often fill with quartz, calcite, or zeolites over millions of years to form amygdales.
Field identification & locations
Identify in the field by its dark weathered exterior, rounded water-worn shape, and distinctive pitted cavities containing secondary minerals.
