igneous
Scoria (Lava Rock)
Scoria (highly vesicular volcanic rock)
Hardness: 5-6 Mohs; Color: reddish-brown; Luster: earthy to sub-metallic; Structure: vesicular (pitted with gas bubbles); Specific Gravity: 2.5-3.0 (but low apparent density)
- Hardness
- 5-6 Mohs
- Color
- reddish-brown
- Luster
- earthy to sub-metallic
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Physical properties
Hardness: 5-6 Mohs; Color: reddish-brown; Luster: earthy to sub-metallic; Structure: vesicular (pitted with gas bubbles); Specific Gravity: 2.5-3.0 (but low apparent density)
Formation & geological history
Formed from basaltic or andesitic magma during volcanic eruptions. As lava is ejected, dissolved gases expand and escape, creating a hole-filled (vesicular) texture as it cools rapidly.
Uses & applications
Commonly used in landscaping as mulch, as a high-temperature insulator in gas grills, in drainage systems, and as an additive in lightweight concrete.
Geological facts
Scoria is often confused with pumice, but scoria is denser, has larger vesicles, and usually sinks in water, whereas pumice typically floats.
Field identification & locations
Identify by its light weight relative to appearance, large visible pores, and sharp, abrasive edges. Commonly found near cinder cones and volcanic vents.
