igneous

Scoria (Lava Rock)

Extrusive Igneous Scoria (Vesicular Basalt)

Hardness: 5-6 Mohs. Color: Dark red, black, or brown. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: Low (often sinks in water, unlike pumice).

Hardness: 5-6 Mohs
Color: Dark red, black, or brown
Luster: Dull/Earthy

Identified March 22, 2026More igneous →

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Physical properties

Hardness: 5-6 Mohs. Color: Dark red, black, or brown. Luster: Dull/Earthy. Structure: Highly vesicular (pitted with gas bubbles). Specific Gravity: Low (often sinks in water, unlike pumice).

Formation & geological history

Formed from gas-rich mafic magma (basaltic) that erupts at the surface. Rapid cooling traps gas bubbles, creating a porous texture. Typically associated with volcanic cinder cones.

Uses & applications

Used widely in landscaping, barbecue grills, high-temperature insulation, drainage systems, and as an additive in lightweight concrete blocks.

Geological facts

Scoria is often confused with pumice, but it is denser and has larger vesicles with thicker walls. Much of the 'lava rock' sold for gas grills and landscaping is actually scoria.

Field identification & locations

Identify by its 'Swiss cheese' appearance and rough, abrasive texture. Commonly found in volcanic regions like the Pacific Northwest, Iceland, and Italy. Often found as loose 'cinders' near volcanic vents.

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Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

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Magnetite

Magnetite (Fe3O4)

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