igneous
Basalt
Aphanitic Mafic Igneous Rock
Hardness: 6 (Mohs); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic) or porphyritic; Specific Gravity: 2.8-3.0.
- Hardness
- 6 (Mohs)
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal Structure: Fine-grained (aphanitic) or porphyritic; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Common in oceanic crust and volcanic regions near tectonic plate boundaries.
Uses & applications
Extensively used in construction for crushed stone, road base, concrete aggregate, and railroad ballast. Also used as dimension stone for counter tops and floor tiles.
Geological facts
Basalt is the most common rock on Earth's surface and also covers large areas of the Moon, Mars, and Venus. It is the primary component of the oceanic crust.
Field identification & locations
Identify by its dark color, high density, and tiny crystals that are usually too small to see with the naked eye. Often exhibits columnar jointing or vesicular (pitted) textures.
