Basalt Pebble

Physical Properties

Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic) or porphyritic; Cleavage: None/Irregular; Specific Gravity: 2.8 - 3.0

Formation & Geological History

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This particular specimen shows rounding due to water erosion (fluvial or beach action).

Uses & Applications

Commonly used in construction as aggregate, for paving stones, 'hot stone' massage therapy, and as decorative landscape elements.

Geological Facts

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

Field Identification & Locations

Identify by its dark color, fine-grained texture (it usually doesn't show visible crystals to the naked eye), and high density. Commonly found in volcanic regions and on beaches where volcanic activity occurred nearby.

Identified on: 4/15/2026

Mode: Standard