igneous
Vesicular Basalt
Basalt with vesicular texture
Hardness: 5-6 (Mohs); Color: Dark grey, greenish-grey, or black; Luster: Dull to sub-metallic; Structure: Aphanitic with vesicles (gas bubbles); Specific Gravity: 2.8–3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey, greenish-grey, or black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey, greenish-grey, or black; Luster: Dull to 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. The holes (vesicles) are created by gas bubbles trapped in the lava as it solidifies. Found in volcanic regions ranging from the Cenozoic era to recent times.
Uses & applications
Used in landscaping, as a construction aggregate, for road base, and sometimes in geological teaching collections.
Geological facts
Vesicular basalt is the terrestrial equivalent of the rocks that make up the lunar maria on the Moon. When vesicles are filled with secondary minerals like calcite or quartz, it is called amygdaloidal basalt.
Field identification & locations
Identify by its dark color, heavy weight compared to pumice, and the presence of small spherical or oval pits. Commonly found in basaltic lava flows in places like Hawaii, Iceland, or the Pacific Northwest.
