igneous
Vesicular Basalt
Basalt (Vesicular)
Hardness 5-6 Mohs; Color: dark grey to brownish-tan (weathered); Luster: dull/earthy; Crystal structure: aphanitic (fine-grained); Porous vesicular texture; High specific gravity.
- Color
- dark grey to brownish-tan (weathered)
- Luster
- dull/earthy
Identified More igneous →
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Physical properties
Hardness 5-6 Mohs; Color: dark grey to brownish-tan (weathered); Luster: dull/earthy; Crystal structure: aphanitic (fine-grained); Porous vesicular texture; High specific gravity.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. The 'holes' are vesicles formed by trapped gas bubbles escaping during solidification.
Uses & applications
Used as aggregate in construction, landscaping, road base, and as decorative stone in aquariums or gardens. Polished varieties are used in 'lava stone' jewelry.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Large vesicles can sometimes later fill with secondary minerals like quartz or calcite to form amygdaloidal basalt.
Field identification & locations
Identify by its pitted, sponge-like surface and heavy weight relative to its size (though vesicles make it lighter than solid basalt). Commonly found in volcanic regions, such as Hawaii, Iceland, or the Pacific Northwest.
