igneous
Basalt
Basalt (Extrusive Igneous Rock)
Hardness: 5-6 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained/Aphanitic (microscopic crystals); Specific Gravity: 2.8-3.0
- Hardness
- 5-6 Mohs
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained/Aphanitic (microscopic crystals); 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 small, weathered fragment of volcanic origin.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, railroad ballast, and in the production of rock wool insulation. Highly durable for construction.
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
Identifiable by its dark color, heavy weight (density), and fine-grained texture. To identify in the field, look for dark, heavy rocks with no visible crystals to the naked eye. Found worldwide in volcanic fields.
