Basalt Pebble

Physical Properties

Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic); High density; Vesicular or smooth depending on erosion.

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. This specific specimen has been water-worn into a smooth pebble shape, likely over thousands of years in a river or coastal environment.

Uses & Applications

Basalt is used extensively in construction (crushed stone, asphalt), for building statues, and as 'hot stones' for massage therapy due to its heat retention properties.

Geological Facts

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

Field Identification & Locations

Identify in the field by its dark color, heavy weight for its size, and absence of visible crystals. Commonly found in volcanic regions, oceanic islands (like Hawaii), and riverbeds in tectonic areas.

Identified on: 4/15/2026

Mode: Standard