Basalt River Pebble

Hardness: 6 (Mohs scale), Color: Dark grey to charcoal, Luster: Dull/Matte, Structure: Fine-grained (aphanitic) with rounded edges due to water erosion, Specific Gravity: 2.8-3.0

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific specimen has been significantly smoothed and rounded by river or coastal water movement over thousands of years.

Commonly used in construction as crushed aggregate, for paving, and in landscaping. Smooth pebbles are often used in decorative water features or for massage therapy.

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.

Identifiable by its weight (denser than most light-colored rocks), fine grain where individual crystals are not visible to the naked eye, and its characteristic dark grey color. Commonly found in riverbeds and on volcanic coastlines.