igneous
Basalt
Aphanitic Mafic Igneous Rock
Hardness: 6 (Mohs scale); Color: dark gray to black; Luster: dull to earthy; Structure: fine-grained (aphanitic); Cleavage: none; Specific Gravity: 2.8 - 3.0.
- Hardness
- 6 (Mohs scale)
- Color
- dark gray to black
- Luster
- dull to earthy
Identified More igneous →
Explore Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs scale); Color: dark gray to black; Luster: dull to earthy; Structure: fine-grained (aphanitic); Cleavage: none; Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (magma) exposed at or very near the Earth's surface. Found in volcanic provinces and oceanic crust.
Uses & applications
Extensively used in construction as aggregate for roads, railroad ballast, and in concrete. Also used for high-quality floor tiles and as a raw material for rock 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
Identified in the field by its dark color, heavy weight (density), and lack of visible crystals to the naked eye. Commonly found in basaltic lava fields or along volcanic shorelines.
