Basalt River Cobble

Hardness: 6 (Mohs), Color: Dark grey to brownish (weathered), Luster: Dull to earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific piece has been rounded by fluvial (river) action.

Basalt is used in construction as aggregate, for paving, and as 'lava rocks' in landscaping. Small river-worn stones are often used in aquariums or as decorative items.

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

Identified by its heavy weight (high specific gravity), dark interior when broken, and lack of visible crystals. Commonly found in former volcanic regions and riverbeds downstream from volcanic sources.