igneous
Vesicular Basalt (River Rock)
Afanitic Vesicular Basalt
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal; Luster: Dull/Sub-metallic; Structure: Aphanitic with vesicles (gas bubbles); Specific Gravity: 2.8–3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to charcoal
- Luster
- Dull/Sub-metallic
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal; Luster: Dull/Sub-metallic; Structure: Aphanitic with vesicles (gas bubbles); Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. The pits (vesicles) are created by gas bubbles escaping as the lava solidifies. The rounded shape indicates water erosion in a river or coastal environment.
Uses & applications
Commonly used in landscaping, as aggregate for concrete and asphalt, and in the manufacturing of rock 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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and the presence of small holes or pits on the surface. Commonly found in volcanic regions or riverbeds downstream from volcanic sites.
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