Basalt Pebble

Hardness of 6 on the Mohs scale, dark gray to black color, dull to sub-metamorphic luster, aphanitic (fine-grained) crystal structure, variable 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 surface of a planet or moon. Geological age can range from recent volcanic eruptions to billions of years old.

Used in construction, as aggregate in concrete, road base, railroad ballast, and sometimes carved for decorative items or monuments.

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

Found globally in volcanic regions, riverbeds, and beaches where wave action has smoothed it into a pebble. Identified by its dark, fine-grained appearance.