igneous
Amygdaloidal Basalt
Vesicular basalt with mineral infillings
AI-generated identification · may be incorrectMohs hardness 5-6, reddish-brown groundmass with light-colored rounded mineral amygdules, aphanitic texture, dull luster.
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Physical properties
Mohs hardness 5-6, reddish-brown groundmass with light-colored rounded mineral amygdules, aphanitic texture, dull luster.
Formation & geological history
Formed from volcanic lava flows where gas bubbles (vesicles) form and are later filled by secondary minerals like quartz or calcite.
Uses & applications
Used primarily in geological study, aggregate construction, and occasionally cut and polished by lapidary collectors.
Geological facts
The distinct round spots are called amygdules, created when hydrothermal fluids deposit minerals into ancient gas cavities.
Field identification & locations
Identify in the field by looking for fine-grained dark volcanic rock speckled with contrasting rounded mineral fillings.
