igneous
Basalt Pebble
Basalt
Hardness: 6.0 on Mohs scale; Color: dark grey to black; Luster: matte/dull; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8–3.0
- Hardness
- 6
- Color
- dark grey to black
- Luster
- matte/dull
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Physical properties
Hardness: 6.0 on Mohs scale; Color: dark grey to black; Luster: matte/dull; 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 exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Primarily used in construction/aggregate, road base, and concrete; worn pebbles like these are often used as decorative landscaping stones or in 'hot stone' massage therapy.
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 in the field by its dark color, heavy weight for its size, and lack of visible crystals. Commonly found on beaches or in river beds where water has rounded the edges of the volcanic rock.
