igneous
Basalt Pebble
Basalt
Hardness (Mohs): 6.0; Color: Dark grey to black; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0
- Color
- Dark grey to black
- Luster
- Dull/Earthy
Identified More igneous →
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Physical properties
Hardness (Mohs): 6.0; Color: Dark grey to black; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); 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 appears to be water-worn into a pebble shape.
Uses & applications
Commonly used as aggregate in construction, road base, and for landscaping. Small pebbles are often used in decorative gardening or as aquarium substrate.
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 on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals. It is ubiquitous in volcanic regions and riverbeds downstream from volcanic mountains.
