igneous
Scoria (Lava Rock)
Scoria (basaltic pyroclastic rock)
Hardness: 5-6 Mohs; Color: Dark red, reddish-brown, or black; Luster: Dull/Sub-metallic; Crystal Structure: Aphanitic/Vesicular; Cleavage: None; Specific Gravity: 0.8-2.1 (low due to air pockets).
- Hardness
- 5-6 Mohs
- Color
- Dark red, reddish-brown, or black
- Luster
- Dull/Sub-metallic
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Physical properties
Hardness: 5-6 Mohs; Color: Dark red, reddish-brown, or black; Luster: Dull/Sub-metallic; Crystal Structure: Aphanitic/Vesicular; Cleavage: None; Specific Gravity: 0.8-2.1 (low due to air pockets).
Formation & geological history
Formed from basaltic or andesitic magma. As gas-rich lava erupts from a volcano, the pressure drops and dissolved gases expand, creating bubbles (vesicles) as the lava cools rapidly. Typically found near volcanic vents.
Uses & applications
Landscaping (decorative stones), drainage material, barbecue grills (heat retention), lightweight concrete aggregate, and abrasive cleaners.
Geological facts
Scoria is often confused with pumice, but it has larger vesicles, thicker walls, and is denser. While pumice can float on water, scoria usually sinks because its cellular structure is heavier and less buoyant.
Field identification & locations
Identified by its highly vesicular (bubbly) texture, dark color (iron-rich), and relatively light weight. Found abundantly in active or dormant volcanic regions like the American West or Hawaii.
