igneous
Amygdoidal Basalt
Extrusive mafic igneous rock with mineral amygdules
AI-generated identification · may be incorrectHardness 6 on Mohs scale for the host rock; dark gray to black color with white or light-colored mineral infills; dull to vitreous luster; microcrystalline structure.
Identified More igneous →
Explore Amygdoidal Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6 on Mohs scale for the host rock; dark gray to black color with white or light-colored mineral infills; dull to vitreous luster; microcrystalline structure.
Formation & geological history
Formed from cooling volcanic lava where gas cavities vesicles later filled with secondary minerals like quartz or calcite.
Uses & applications
Used in aggregate for construction, road building, and occasionally tumbled as a decorative specimen by collectors.
Geological facts
The spots are ancient gas bubbles trapped in lava that filled with groundwater minerals over millions of years.
Field identification & locations
Identify by the dark, fine-grained volcanic matrix dotted with contrasting rounded mineral spots; common worldwide in ancient lava flows.
