igneous
Lava Rock (Scoria)
Scoria (Mafic volcanic rock)
Hardness: 5-6 Mohs; Color: Black, dark gray, dark brown, or reddish-brown; Luster: Dull or submetallic; Structure: Highly vesicular/porous; Cleavage: None; Specific Gravity: varies (low due to air pockets)
- Hardness
- 5-6 Mohs
- Color
- Black, dark gray, dark brown, or reddish-brown
- Luster
- Dull or submetallic
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Physical properties
Hardness: 5-6 Mohs; Color: Black, dark gray, dark brown, or reddish-brown; Luster: Dull or submetallic; Structure: Highly vesicular/porous; Cleavage: None; Specific Gravity: varies (low due to air pockets)
Formation & geological history
Formed from gas-rich, mafic magma cooling rapidly near the surface of a volcano. The holes (vesicles) are formed by trapped gas bubbles that expand as the pressure drops during eruption.
Uses & applications
Used widely in landscaping, gas grills, aquarium filtration, hot stone massages, and as an additive in lightweight concrete.
Geological facts
Scoria is different from pumice because scoria is mafic (dark-colored) and denser, whereas pumice is felsic and often floats on water. Most lava rocks are found in young volcanic fields.
Field identification & locations
Identify by its dark color, lightweight feel compared to solid basalt, and numerous visible holes or vesicles. Commonly found in volcanic regions like Iceland, Hawaii, and the Western US.
