igneous
Scoria (Lava Rock)
Scoria
Hardness: 5-6 (Mohs scale); Color: Dark brown, black, or reddish-brown; Luster: Dull/Sub-vitreous; Structure: Vesicular (full of air bubbles); Specific Gravity: Relatively low due to porosity.
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark brown, black, or reddish-brown
- Luster
- Dull/Sub-vitreous
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark brown, black, or reddish-brown; Luster: Dull/Sub-vitreous; Structure: Vesicular (full of air bubbles); Specific Gravity: Relatively low due to porosity.
Formation & geological history
Formed from volcanic eruptions where gas-rich, mafic magma cools rapidly, trapping air bubbles inside. Often found in volcanic cinder cones and lava flows.
Uses & applications
Used in landscaping, high-temperature insulation, drainage rock, gas grill briquettes, and as lightweight aggregate in concrete.
Geological facts
Scoria is different from pumice because it is denser and has larger vesicles; it also usually originates from basaltic or andesitic magma rather than rhyolitic magma.
Field identification & locations
Look for a highly porous, 'bubbly' texture that is rough to the touch. It is heavier than pumice and will usually sink in water, unlike most pumice specimens.
