Igneous

Scoria (Red Lava Rock)

Scoria (Extrusive Igneous Rock)

Hardness: 5-6 (Mohs scale); Color: Dark red to reddish-brown (oxidized iron); Luster: Dull to sub-vitreous; Structure: Highly vesicular (pitted/bubbly); Specific Gravity: 0.8-2.1 (lightweight/often floats)

Hardness: 5-6 (Mohs scale)
Color: Dark red to reddish-brown (oxidized iron)
Luster: Dull to sub-vitreous

Identified March 29, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling and depressurization of gas-rich basaltic or andesitic magma ejected from a volcano. The holes (vesicles) are created by trapped gas bubbles that expand during eruption.

Uses & applications

Used extensively in landscaping, gas grill lava rocks, lightweight concrete aggregate, high-temperature insulation, and aquarium decor.

Geological facts

Scoria is often confused with pumice, but it has thicker cell walls and is denser; while some scoria floats, most eventually sinks. The red color is caused by the oxidation of iron within the magma during eruption.

Field identification & locations

Identify by its 'sponge-like' appearance, rough/abrasive texture, and light weight. Commonly found near cinder cones and volcanic vents in regions like Arizona, Iceland, and Italy.

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Dark Igneous Rock (Likely Basalt or Diabase)

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

Iron(II,III) oxide (Fe3O4)

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Magnetite (Fe3O4)

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