igneous
Basalt
Extrusive Igneous Rock (Mafic)
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to aphantic (fine-grained). Crystal Structure: Typically fine-grained/microcrystalline. Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black
- Luster
- Dull to aphantic (fine-grained)
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to aphantic (fine-grained). Crystal Structure: Typically fine-grained/microcrystalline. 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 rock in Earth's crust.
Uses & applications
Used primarily in construction for aggregate, road base, railroad ballast, and decorative garden stones. Some varieties are used in 'hot stone' massage therapy.
Geological facts
Basalt is the primary rock of the ocean floor. It is also found on the Moon, Mars, and Venus. The Giant's Causeway in Ireland is a famous example of columnar basalt.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and lack of visible crystals to the naked eye. It is commonly found in volcanic regions and oceanic crustal plates.
