Scoria (Lava Rock)

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.

Identified on: 4/15/2026

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