Basalt Pebble

Hardness of 6 on the Mohs scale, dark gray to black color, dull to sub-vitreous luster, fine-grained (aphanitic) crystal structure, specific gravity around 2.8-3.0.

Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface, often originating from volcanic activity.

Used in construction as crushed aggregate, railroad ballast, road base, and occasionally in stone masonry or as tumbled stones.

Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also abundantly found on the surfaces of the Moon and Mars.

Identified by its dark color, heavy feel for its size, and extremely fine-grained texture where individual crystals are typically not visible to the naked eye. Found worldwide in volcanic regions and river beds.