igneous
Vesicular Basalt (Scoria)
Vesicular Basalt
Hardness: 5-6 Mohs; Color: Black, dark gray, or dark brown; Luster: Dull to sub-metallic; Structure: Aphanitic (fine-grained) with vesicles (gas bubbles); Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Black, dark gray, or dark brown
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: Black, dark gray, or dark brown; Luster: Dull to sub-metallic; Structure: Aphanitic (fine-grained) with vesicles (gas bubbles); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the rapid cooling of mafic lava rich in dissolved gases. As the lava erupts, gas bubbles expand and become trapped as the rock solidifies. Typical of volcanic eruptions worldwide.
Uses & applications
Commonly used in landscaping, as a drainage material, in gas grills as 'lava rocks', and in lightweight concrete production.
Geological facts
The holes in the rock, called vesicles, are effectively frozen gas bubbles that were once trapped in molten lava. 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 color, heavy weight (relative to size, though vesicles can make it feel lighter), and characteristic Swiss-cheese-like holes. Found near active or extinct volcanic fields.
