igneous
Scoria (Lava Rock)
Vesicular Basalt / Scoria
Mohs hardness: 5-6; Color: dark gray to black; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained) with many vesicles (holes); Specific gravity: low (often floats initially in water before it saturates).
- Hardness
- 5-6
- Color
- dark gray to black
- Luster
- dull to sub-metallic
Identified More igneous →
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Physical properties
Mohs hardness: 5-6; Color: dark gray to black; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained) with many vesicles (holes); Specific gravity: low (often floats initially in water before it saturates).
Formation & geological history
Formed from extrusive volcanic activity where gas is trapped in cooling mafic magma, creating a vesicular texture. Usually associated with cinder cones and basaltic flows from the Cenozoic era to recent volcanic events.
Uses & applications
Used extensively in landscaping, gas grills (lava rocks), high-temperature insulation, drainage rock, and as an abrasive in stone-washing textiles.
Geological facts
Scoria is different from pumice because it has larger vesicles and thicker cell walls, making it denser. It is a primary component of cinder cone volcanoes like those found in Sunset Crater, Arizona.
Field identification & locations
Identify by its 'Swiss cheese' appearance, dark color, and lightweight feel compared to solid basalt. Commonly found near volcanic fields in the Western United States, Iceland, and Italy.
