igneous
Scoria
Vesicular Basalt
Hardness: 5-6 Mohs. Color: Reddish-brown, dark grey, or black. Luster: Dull, earthy. Structure: Highly vesicular (honeycombed with air bubbles). Specific Gravity: 2.5-3.0 (though it can feel lighter due to porosity).
- Hardness
- 5-6 Mohs
- Color
- Reddish-brown, dark grey, or black
- Luster
- Dull, earthy
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Physical properties
Hardness: 5-6 Mohs. Color: Reddish-brown, dark grey, or black. Luster: Dull, earthy. Structure: Highly vesicular (honeycombed with air bubbles). Specific Gravity: 2.5-3.0 (though it can feel lighter due to porosity).
Formation & geological history
Formed through the rapid cooling of basaltic or andesitic lava rich in dissolved gases. As the lava erupts, the gases expand and escape, leaving behind a porous, hole-filled texture. Primarily found in volcanic cinder cones.
Uses & applications
Commonly used in landscaping (lava rock), as high-temperature insulation, in gas grills to distribute heat, and as a lightweight aggregate in concrete or for traction on icy roads.
Geological facts
Unlike pumice, which is also a volcanic rock with air pockets, scoria usually sinks in water because it has thicker cell walls and a higher density.
Field identification & locations
Identify by its very rough, sharp texture and numerous visible pores (vesicles). It is typically darker and heavier than pumice. Common in volcanic regions such as Iceland, Hawaii, and Arizona.
