igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0; Cleavage: None, often demonstrates conchoidal fracture.
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0; Cleavage: None, often demonstrates conchoidal fracture.
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 volcanic rock on Earth.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and floor tiles. It is also used in the manufacturing of stone wool insulation and occasionally for statues or jewelry like 'Lava Stone'.
Geological facts
Basalt underlies more of Earth's surface than any other rock type. Most areas within Earth's ocean basins are underlain by basalt. It also makes up the lunar maria on the Moon.
Field identification & locations
Identify in the field by its dark color, heavy weight (relative to size), and very fine grains that are usually not visible to the naked eye. Found worldwide in volcanic regions such as the Giant's Causeway or the Hawaiian Islands.
