igneous
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6.0; Color: Dark gray to black; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic) microcrystalline; Cleavage: None; Specific Gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6.0; Color: Dark gray to black; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic) microcrystalline; Cleavage: None; Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed through the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Used primarily in construction for road base, concrete aggregate, railroad ballast, and occasionally as structural stone or in the manufacture of stone 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 found on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and lack of visible crystals. Commonly found in regions with volcanic history or near coastal basalt columns.
