igneous

Scoria

Vesicular Basaltic Glass (comprised primarily of volcanic glass/silica with plagioclase, pyroxene, and olivine crystals)

Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown or black. Luster: Dull to sub-vitreous. Texture: Vesicular (highly porous/holey). Specific gravity: Relatively light but usually sinks in water (unlike pumice).

Hardness: 5-6 Mohs
Color: Reddish-brown to dark brown or black
Luster: Dull to sub-vitreous

Identified March 29, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich basaltic or andesitic magma expelled during explosive volcanic eruptions. As the lava cools rapidly at the surface (extrusive), trapped gas bubbles create open cavities called vesicles.

Uses & applications

Commonly used in landscaping (lava rocks), as an abrasive in high-friction footwear/soles, in gas grills for heat retention, and as lightweight aggregate for concrete or drainage systems.

Geological facts

Scoria is often confused with pumice; however, scoria has thicker vesicle walls and is denser, meaning it typically sinks in water while pumice floats. Its red color is usually caused by the oxidation of iron within the lava.

Field identification & locations

Identify by its 'sponge-like' appearance, rough texture, and many visible holes. Found in volcanic regions like the American West (Iceland, Italy, Hawaii). Collectors look for vibrant red hues or pieces containing visible crystals like olivine.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

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Magnetite

Magnetite (Fe3O4)

mineral