igneous
Basalt
Basalt (principally Plagioclase Feldspar and Pyroxene)
Hardness: 6.0-6.5 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8-3.0.
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6.0-6.5 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8-3.0.
Formation & geological history
Extrusive volcanic formation where mafic lava cools rapidly at or near the surface. These specimens are found across all geological ages from the Archean to the present day.
Uses & applications
Used extensively in construction as road base, concrete aggregate, and railroad ballast. Also used as floor tiles, Monuments, and increasingly as a medium for absorbing CO2 via mineral carbonation.
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, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. It often shows occasional small holes (vesicles) from gas bubbles. Found worldwide in volcanic regions like the Pacific Northwest, Hawaii, and Iceland.
