Basalt Pebble

Hardness: 6 (Mohs scale), Color: Dark gray to charcoal, Luster: Dull/Matte, Structure: Fine-grained (aphanitic), Specific Gravity: 2.8-3.0

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen has been rounded by fluvial or marine water erosion.

Used extensively in construction as aggregate, road base, and ballast. Smaller pebbles are common in landscaping and 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.

Identify by its dark color, heavy weight for its size, and lack of visible large crystals. Commonly found on beaches or in riverbeds in volcanic regions.