igneous
Scoria
Vesicular Basaltic Rock
Mohs hardness: 5-6; Color: Reddish-brown to black; Luster: Dull/Sub-vitreous; Structure: Vesicular (highly porous); Cleavage: None; Specific Gravity: 0.8-2.1 (low, though it often sinks)
- Hardness
- 5-6
- Color
- Reddish-brown to black
- Luster
- Dull/Sub-vitreous
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Physical properties
Mohs hardness: 5-6; Color: Reddish-brown to black; Luster: Dull/Sub-vitreous; Structure: Vesicular (highly porous); Cleavage: None; Specific Gravity: 0.8-2.1 (low, though it often sinks)
Formation & geological history
Formed during explosive volcanic eruptions where trapped gases expand and form bubbles as magma cools rapidly. Typically associated with cinder cones and basaltic flows.
Uses & applications
Commonly used in landscaping as decorative 'lava rock,' as an aggregate in lightweight concrete, for drainage, and in gas grills for heat retention.
Geological facts
Scoria is technically an extrusive igneous rock. Unlike pumice, which is also vesicular, scoria typically has larger holes and is denser, preventing it from floating on water for long.
Field identification & locations
Identify by its rough, hole-filled (vesicular) texture and lightweight feel. Commonly found in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
