igneous
Basalt
Basalt
Hardness: 5-6 (Mohs); Color: Dark gray to black, often weathering to green or brown; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark gray to black, often weathering to green or brown
- Luster
- Dull/earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark gray to black, often weathering to green or brown; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0
Formation & geological history
Extrusive volcanic formation; created from the rapid cooling of magnesium-rich and iron-rich lava at or very near the surface of a planet or moon; can be any geological age from Hadean to modern.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Also used for stone carving and as a heat sink in volcanic stone massages.
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 prevalent on the Moon and Mars.
Field identification & locations
Identify by its heavy weight, dark color, and lack of visible crystals to the naked eye. Found worldwide in volcanic fields and oceanic crust outcrops.
