igneous
Vesicular Basalt
Basalt (principally Plagioclase and Pyroxene)
Hardness: 6-7 on Mohs scale; Color: Dark grey to black, often weathering to brown/red; Luster: Dull to earthy; Texture: Vesicular (contains small cavities or gas bubbles); Crystal structure: Aphanitic (fine-grained).
- Hardness
- 6-7 on Mohs scale
- Color
- Dark grey to black, often weathering to brown/red
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey to black, often weathering to brown/red; Luster: Dull to earthy; Texture: Vesicular (contains small cavities or gas bubbles); Crystal structure: Aphanitic (fine-grained).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. The vesicles are formed by gas bubbles that were trapped in the lava as it cooled.
Uses & applications
Used in construction as aggregate, for road base, concrete, and railroad ballast. Larger decorative pieces are used in landscaping and as 'lava rocks' for grills.
Geological facts
Basalt is the most common rock in 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 in the field by its dark color, heavy weight relative to size (high density), and the presence of small holes (vesicles). Found in volcanic regions such as the Pacific Northwest or Hawaii.
