igneous
Basalt
Basalt (dominated by Plagioclase and Pyroxene)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained), often vesicular or porphyritic; Specific Gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained), often vesicular or porphyritic; Specific Gravity: 2.8 - 3.0
Formation & geological history
Extrusive volcanic formation; formed from the rapid cooling of low-viscosity basaltic lava. Found in oceanic crust, volcanic islands, and flood basalt provinces.
Uses & applications
Extensively used as aggregate in construction, road base, concrete, and railroad ballast. Also used for decorative landscaping and stone masonry.
Geological facts
Basalt is the most common rock type in the Earth's crust and covers most of the ocean floors. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, fine-grained texture, and high density. Commonly found on beaches as rounded river or sea stones like this specimen.
