igneous
Amygdaloidal basalt
Vesicular basalt with secondary mineral-filled amygdules; the green fillings may be chlorite, epidote, or prehnite
AI-generated identification · may be incorrectFine-grained, brown weathered matrix with rounded green mineral patches. Basalt is typically plagioclase and pyroxene, Mohs hardness about 6; the visible fillings cannot be identified confidently from the image.
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Physical properties
Fine-grained, brown weathered matrix with rounded green mineral patches. Basalt is typically plagioclase and pyroxene, Mohs hardness about 6; the visible fillings cannot be identified confidently from the image.
Formation & geological history
Formed as gas-rich lava cooled at or near the surface; later fluids deposited minerals in its cavities. The specimen’s age and exact locality cannot be determined from appearance alone.
Uses & applications
Commonly collected as a specimen; basalt is also widely used as crushed aggregate and building stone.
Geological facts
The rounded mineral-filled cavities are called amygdules, distinguishing amygdaloidal basalt from ordinary vesicular basalt.
Field identification & locations
Look for a dense, fine-grained dark volcanic matrix containing rounded contrasting fillings. Green patches are consistent with several secondary minerals, so locality or testing is needed for a firm identification.
