igneous
Basalt with Amygdules
Extrusive mafic igneous rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale for the secondary mineral infillings, dark gray to brownish matrix, dull luster, microcrystalline to aphanitic texture.
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Physical properties
Hardness of 6 on the Mohs scale for the secondary mineral infillings, dark gray to brownish matrix, dull luster, microcrystalline to aphanitic texture.
Formation & geological history
Formed from rapidly cooling mafic lava flows where gas bubbles created vesicles later filled by secondary mineral precipitation like quartz or calcite.
Uses & applications
Used in aggregate for construction, railroad ballast, and occasionally in lapidary work when decorative mineral infillings are present.
Geological facts
Vesicles in basalt often become filled with groundwater minerals to form agates, jaspers, or zeolites over long geological periods.
Field identification & locations
Identify by a dark, fine-grained volcanic matrix featuring distinct rounded mineral pockets or nodules. Commonly found in ancient and modern volcanic provinces worldwide.
