igneous
Basalt
Extrusive mafic igneous rock
Hardness: 6 Mohs; Color: dark grey to black; Luster: dull to earthy; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8-3.0; Contains plagioclase feldspar and pyroxene.
- Hardness
- 6 Mohs
- Color
- dark grey 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; Color: dark grey to black; Luster: dull to earthy; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8-3.0; Contains plagioclase feldspar and pyroxene.
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. It is the most common rock type in the Earth's crust (oceanic crust).
Uses & applications
Extensively used in construction, especially as crushed stone for road base, railroad ballast, and concrete aggregate. Also used for high-temperature insulation (rock wool) and as decorative garden stones.
Geological facts
Basaltic lava is the most common volcanic rock on Earth and also makes up the lunar maria on the Moon and much of the surface of Mars and Venus.
Field identification & locations
Identify in the field by its dark color, heavy weight (density), and fine-grained texture with occasional small vesicles (holes from gas bubbles). It is ubiquitous in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
