igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull/earthy to sub-metallic
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy to sub-metallic; Crystal structure: Aphanitic (fine-grained); 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.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Can be used in stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. It often breaks into angular fragments. Common in volcanic regions.
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Dark Igneous Rock (Likely Basalt or Diabase)
Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.
Igneous