igneous
Basalt
Basalt
Hardness: 6.0-7.0 on Mohs scale; Color: Black, dark gray, or dark green; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) to porphyritic; Specific Gravity: 2.8-3.0.
- Hardness
- 6
- Color
- Black, dark gray, or dark green
- Luster
- Dull to sub-metallic
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.0-7.0 on Mohs scale; Color: Black, dark gray, or dark green; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) to porphyritic; 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. Most common on Earth's oceanic crust.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for floor tiles or monuments. High-quality specimens are used in stone healing and architectural design.
Geological facts
Basalt is the most common volcanic rock on Earth and also covers vast areas of the Moon, Mars, and Venus. On the Moon, the dark plains known as 'maria' are actually massive basaltic lava flows.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture with no visible crystals to the naked eye. Often exhibits vesicular (bubbly) textures or columnar jointing in the field.
