igneous
Basalt Pebble
Basalt (Mafic volcanic rock)
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, Crystal structure: Fine-grained/Aphanitic, Cleavage: None, Specific gravity: 2.8–3.0
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, Crystal structure: Fine-grained/Aphanitic, Cleavage: None, 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 specific specimen has been rounded by fluvial or coastal erosion.
Uses & applications
Commonly used in construction aggregate, road base, and as decorative landscaping stones; fine basalt is also used in high-strength industrial flooring.
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 found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible large crystals. Commonly found in former volcanic regions and riverbeds.
