Igneous
Basalt (Polished)
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6\u20137 Mohs; Color: Dark grey to black; Luster: Dull (naturally) to Sub-vitreous (when polished); Crystal structure: Fine-grained/Aphanitic; Specific gravity: 2.8\u20133.0
- Hardness
- 6\u20137 Mohs
- Color
- Dark grey to black
- Luster
- Dull (naturally) to Sub-vitreous (when polished)
Identified More igneous →
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Physical properties
Hardness: 6\u20137 Mohs; Color: Dark grey to black; Luster: Dull (naturally) to Sub-vitreous (when polished); Crystal structure: Fine-grained/Aphanitic; Specific gravity: 2.8\u20133.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the surface of Earth. It is the most common rock in the Earth's crust, found in oceanic plates and large volcanic provinces.
Uses & applications
Used in construction (as aggregate or road base), decorative landscaping, 'hot stone' massage therapy, and occasionally for carved polished figurines or jewelry.
Geological facts
Basalt is also found on other planets, including Mars and Venus, and makes up the vast majority of the lunar maria (the dark plains on the moon).
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and lack of visible crystals to the naked eye. In the field, it often forms distinct hexagonal columns if part of a large flow.
