igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull/Matte
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/Matte; 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. This specimen appears to be a water-worn river stone.
Uses & applications
Used primarily in construction for aggregate, road base, and railroad ballast. Fine-grained specimens are also used for stone massage and decorative landscaping.
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, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and lack of visible crystals to the naked eye. Often found in volcanic regions or as rounded pebbles in riverbeds.
