igneous
Basalt
Basalt (principally Plagioclase Feldspar and Pyroxene)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained (aphanitic); 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. Basalt comprises more than 90% of all volcanic rock on Earth.
Uses & applications
Extensively used in construction as aggregate for road base, concrete, and railroad ballast. It is also used as dimension stone for flooring and monuments.
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 (relative to size), and fine-grained texture lacking large visible crystals. It is found in volcanic regions worldwide, particularly near oceanic ridges and hotspots like Hawaii.
