igneous
Scoria (Basaltic Lava Rock)
Vesicular Basalt
Hardness: 5-6 (Mohs scale); Color: Black, dark gray, or reddish-brown; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) with a vesicular texture; Cleavage: None; Specific Gravity: Relatively low due to gas bubbles (vesicles).
- Hardness
- 5-6 (Mohs scale)
- Color
- Black, dark gray, or reddish-brown
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Black, dark gray, or reddish-brown; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained) with a vesicular texture; Cleavage: None; Specific Gravity: Relatively low due to gas bubbles (vesicles).
Formation & geological history
Formed from extrusive volcanic activity where gas is trapped in cooling magma, creating many small holes. It is common in areas of recent volcanic activity (Quaternary period to present) such as cinder cones.
Uses & applications
Used in landscaping (lava rocks), BBQ grills, high-temperature insulation, lightweight concrete aggregate, and as a drainage material.
Geological facts
Scoria is often mistaken for pumice; however, scoria sinks in water because it has thicker cell walls and a more mafic composition, whereas pumice is more silicic and can float.
Field identification & locations
Identify by its dark color, high porosity with visible holes (vesicles), and rough, abrasive texture. Commonly found near volcanoes and mid-ocean ridges.
