Basalt Pebble

Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity around 2.8 to 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 shaped into a smooth pebble by water action in a river or beach environment

Used in construction as crushed stone, aggregate for concrete and asphalt, railroad ballast, and sometimes in landscaping or stone massage

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

Can be identified in the field by its dark color, heavy feel relative to its size, and fine-grained texture where individual crystals are typically too small to see without a microscope; commonly found near volcanic regions, rivers, and coastlines