igneous
Amygdaloidal Basalt
Extrusive mafic igneous rock with secondary mineral infillings
AI-generated identification · may be incorrectHardness 6 on Mohs scale for the filling minerals, dark brown to black color, dull to vitreous luster, aphanitic crystal structure.
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Physical properties
Hardness 6 on Mohs scale for the filling minerals, dark brown to black color, dull to vitreous luster, aphanitic crystal structure.
Formation & geological history
Formed from cooling volcanic lava where gas bubbles formed vesicles, later filled by secondary minerals like quartz or calcite.
Uses & applications
Used primarily in crushed stone for construction, road aggregate, and geological collections.
Geological facts
The distinctive rounded holes are vesicles formed by trapped gas, some of which become amygdules when filled with secondary minerals.
Field identification & locations
Identify by dark, fine-grained volcanic matrix containing rounded cavities or mineral-filled spots; found in volcanic regions worldwide.
