igneous
Basalt
Basalt (dominated by Plagioclase Feldspar and Pyroxene)
Hardness: 6; Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), typically contains micro-crystals; Specific gravity: 2.8 - 3.0.
- Hardness
- 6
- Color
- dark grey to black
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6; Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), typically contains micro-crystals; Specific gravity: 2.8 - 3.0.
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. Most common rock on Earth's crust.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Sometimes used in sculpture or as polished tiles.
Geological facts
Basalt is the primary rock type making up the ocean floors and is also found extensively on the Moon and Mars. It can form unique hexagonal columns during cooling, known as columnar jointing.
Field identification & locations
Identify by its heavy weight (density), dark color, and very fine-grained texture. It often shows water-worn, dull surfaces when found as river or beach pebbles like this specimen.
