igneous
Amygdaloidal Basalt
Mafic extrusive igneous rock with secondary mineral infills
AI-generated identification · may be incorrectHardness of 5-6 on the Mohs scale, grayish-green color due to altered minerals, dull to sub-vitreous luster, with distinctive vesicular cavities filled with secondary minerals.
Identified More igneous →
Explore Amygdaloidal Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 5-6 on the Mohs scale, grayish-green color due to altered minerals, dull to sub-vitreous luster, with distinctive vesicular cavities filled with secondary minerals.
Formation & geological history
Formed from cooling volcanic lava flows where gas bubbles created vesicles later filled by mineral-rich groundwater, highly consistent with the basalt flows of the Pacific Northwest.
Uses & applications
Used primarily in aggregate, construction, and road metal, though specimens with attractive amygdules are collected by rockhounds.
Geological facts
Vesicles in this specimen were formed by trapped volcanic gases and later mineralized, fitting the regional geology of Washington state basalt formations.
Field identification & locations
Identify in the field by its dark volcanic matrix peppered with rounded mineral-filled cavities. Common in volcanic regions worldwide.
