igneous
Basalt Pebble
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull or matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull or matte
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull or 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 at or very near the Earth's surface. These specimens are often water-worn in riverbeds or coastal environments.
Uses & applications
Basalt is used extensively in construction as aggregate for concrete and asphalt, as well as in the manufacturing of rock wool insulation.
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 common on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight for its size, and absence of visible crystals without a lens. Found globally in volcanic regions and river deposits.
