igneous
Vesicular basalt pebble with pale mineral infill
Basalt, likely amygdaloidal basalt; vesicles may contain calcite, zeolite, or silica
AI-generated identification · may be incorrectDark gray-black, fine-grained and matte, with rounded gas cavities and irregular white to cream fillings; hardness about 5–6 for the basalt, while infill minerals may be softer or harder. Typically massive, with no visible cleavage; specific gravity about 2.8–3.0.
Identified More igneous →
Explore Vesicular basalt pebble with pale mineral infill in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-black, fine-grained and matte, with rounded gas cavities and irregular white to cream fillings; hardness about 5–6 for the basalt, while infill minerals may be softer or harder. Typically massive, with no visible cleavage; specific gravity about 2.8–3.0.
Formation & geological history
Formed when fluid basaltic lava cooled rapidly at or near Earth’s surface, trapping volcanic gas bubbles; later groundwater deposited minerals in the cavities. The exact geological age cannot be determined from the photograph.
Uses & applications
Used mainly as decorative stone, landscaping aggregate, and a collector specimen; polished examples can be attractive but are usually low-value.
Geological facts
The filled cavities are called amygdules, distinguishing amygdaloidal basalt from ordinary vesicular basalt. White fillings commonly include calcite, quartz, or zeolite-group minerals.
Field identification & locations
Identify by its black fine-grained volcanic matrix, low density relative to many crystalline rocks, vesicles, and possible reaction to dilute hydrochloric acid if the white infill is calcite. Common in volcanic regions and basaltic river or beach gravels.
