igneous

Scoria (Lava Rock)

Aphanitic vesicular mafic igneous rock

Hardness: 5-6 Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthly; Structure: Vesicular (full of holes); Cleavage: None/Conchoidal; Specific Gravity: 0.8-2.1 (low due to air pockets)

Hardness: 5-6 Mohs scale
Color: Reddish-brown to dark brown
Luster: Dull/Earthly

Identified March 15, 2026More igneous →

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Physical properties

Hardness: 5-6 Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthly; Structure: Vesicular (full of holes); Cleavage: None/Conchoidal; Specific Gravity: 0.8-2.1 (low due to air pockets)

Formation & geological history

Formed through the rapid cooling of gas-rich basaltic or andesitic lava ejected from a volcano. The holes (vesicles) are created by expanding gas bubbles trapped during solidifcation. Found in cinder cones and volcanic fields.

Uses & applications

Used in landscaping for drainage and decoration, gas grills (lava rocks), lightweight concrete production, road surfacing, and high-temperature insulation.

Geological facts

Scoria is similar to pumice, but it is denser and has larger vesicles with thicker walls. Unlike some pumice, most scoria specimens will sink in water because they have a higher specific gravity and iron content.

Field identification & locations

Identify by its 'sponge-like' appearance, rough texture, and lightweight feel. It is commonly found in regions of recent volcanic activity like Arizona, Hawaii, Iceland, and Italy. Look for its characteristic red or black color and sharp edges.

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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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