igneous
Basalt with Vesicular Texture
Basalt (SiO2 range 45-52%)
Hardness: 6 (Mohs scale); Color: Dark grey to black, greenish-black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0.
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black, greenish-black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black, greenish-black; Luster: Dull 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 at or very near the Earth's surface. This specimen appears water-worn, likely found in a riverbed or coastal area.
Uses & applications
Commonly used as crushed stone for road bases, concrete aggregate, and railroad ballast. Also used in high-quality basalt fiber for insulation and automotive parts.
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 heavy weight (density), dark color, and presence of tiny holes (vesicles). Found in volcanic regions or river beds carrying volcanic runoff.
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