igneous
Scoria (Lava Rock)
Scoria (vesicular mafic igneous rock)
Hardness: 5-6 Mohs. Color: black to dark gray. Luster: dull to earthy. Structure: highly vesicular (porous). Cleavage: none. Specific gravity: low (2.0-3.0) but typically sinks in water.
- Hardness
- 5-6 Mohs
- Color
- black to dark gray
- Luster
- dull to earthy
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Physical properties
Hardness: 5-6 Mohs. Color: black to dark gray. Luster: dull to earthy. Structure: highly vesicular (porous). Cleavage: none. Specific gravity: low (2.0-3.0) but typically sinks in water.
Formation & geological history
Formed from the rapid cooling of basaltic or andesitic magma. Gas bubbles (vesicles) are trapped as the lava solidifies near the surface of volcanic vents or flows.
Uses & applications
Widely used in landscaping, gas grills, hydroponics, lightweight concrete aggregate, and as high-friction material on icy roads.
Geological facts
Unlike pumice, scoria has thicker vesicle walls and is denser, causing it to sink in water. It is a common component of cinder cones.
Field identification & locations
Identify by its dark color, lightweight feel compared to solid rock, and abundance of small visual holes. Commonly found in volcanic fields like those in Iceland, Hawaii, or it can be found at garden supply stores.
