igneous
Vesicular Basalt (or Scoraceous Basalt)
Basalt (Vesicular texture)
Hardness: 5-6 (Mohs); Color: Dark grey to black (weathered to light tan/white in salt environments); Luster: Dull/Earthy; Structure: Fine-grained aphanitic with numerous voids (vesicles) caused by trapped gas; Specific Gravity: 2.8 - 3.0.
- Hardness
- 5-6 (Mohs)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to black (weathered to light tan/white in salt environments); Luster: Dull/Earthy; Structure: Fine-grained aphanitic with numerous voids (vesicles) caused by trapped gas; Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The pitted texture is created as gas bubbles (volatiles) escape during solidification. This process is common in volcanic eruptions from the Cenozoic era to the present.
Uses & applications
Used in landscaping, as an aggregate in construction (road base/concrete), for BBQ grill stones, and occasionally for 'pumice stone' type abrasive skin care if highly vesicular.
Geological facts
The holes in the rock are called vesicles; when these holes later fill with minerals like quartz or calcite, the rock is called an amygdaloidal basalt. Basalt is the most common rock type in the Earth's crust and makes up the ocean floors.
Field identification & locations
Identify by its dark interior, high density (for a rock with holes), and the presence of round or oval voids. Common along volcanic coastlines (e.g., Hawaii, Iceland, Pacific Northwest). To identify in the field, look for 'peppered' or 'holy' textures in dark, heavy stones.
