igneous
Vesicular Basalt / Scoria (with Iron Oxide Alteration)
Vesicular Basalt
AI-generated identification · may be incorrectHardness: 5.5-6 on Mohs scale; Color: Dark grey to black base with tan, orange, and reddish-brown iron-oxide weathering; Luster: Earthy to dull; Texture: Aphanitic with prominent spherical to irregular vesicles (gas bubbles); Cleavage: None.
- Hardness
- 5
- Luster
- Earthy to dull
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Physical properties
Hardness: 5.5-6 on Mohs scale; Color: Dark grey to black base with tan, orange, and reddish-brown iron-oxide weathering; Luster: Earthy to dull; Texture: Aphanitic with prominent spherical to irregular vesicles (gas bubbles); Cleavage: None.
Formation & geological history
Formed through the rapid cooling of low-viscosity, gas-rich basaltic lava erupted at or near the Earth's surface. As pressure drops during eruption, dissolved gases expand into bubbles (vesicles) that become trapped as the silicate lava solidifies rapidly.
Uses & applications
Used in landscaping, construction aggregates, drainage systems, BBQ lava rocks, and as educational geological study specimens.
Geological facts
The open holes (vesicles) in basaltic lava are formed by escaping gas bubbles, mainly steam and carbon dioxide. Vesicular rocks with high porosity often float briefly in water or act as natural filters.
Field identification & locations
Identify in the field by its sponge-like or pitted vesicular surface, dark host rock, light weight relative to solid basalt, and reddish-tan surface oxidation. Commonly found near volcanic fields, rift valleys, oceanic crust formations, and volcanic islands worldwide.
