Vesicular Basalt

Hardness of 6 on the Mohs scale, dark brown to black color, dull to sub-aphanitic luster, aphanitic (fine-grained) groundmass with prominent vesicles (gas cavities), specific gravity around 2.8-3.0.

Formed from low-viscosity mafic lava that erupted onto the Earth's surface and cooled rapidly, allowing trapped volcanic gases to escape and leave behind holes (vesicles). Geological age ranges from recent volcanic eruptions to billions of years old.

Used in construction, as crushed stone for road bases, railroad ballast, landscaping, and sometimes in lightweight aggregate concrete or spa stones.

Vesicular basalt is one of the most common rock types on Earth's surface and also makes up a vast majority of the oceanic crust as well as volcanic plains on the Moon and Mars.

Easily identified by its dark color, fine-grained texture, and characteristic pitted or sponge-like appearance due to gas bubbles. Found worldwide in volcanic regions, rift zones, and oceanic islands.