igneous

Scoria (Vesicular Basalt)

Scoria (Vesicular Igneous Rock)

Hardness: 5-6 (Mohs). Color: dark reddish-brown, black, or dark gray. Luster: dull to sub-metallic. Texture: highly vesicular (pitted with gas bubbles), fine-grained (aphanitic), jagged edges. Specific Gravity: relatively low due to porosity.

Hardness: 5-6 (Mohs)
Color: dark reddish-brown, black, or dark gray
Luster: dull to sub-metallic

Identified March 18, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the rapid cooling of basaltic or andesitic lava containing high amounts of dissolved gases. As the lava erupts, the pressure drops and gases expand to create vesicles (holes) before the rock solidifies. Found in volcanic regions of all ages.

Uses & applications

Commonly used in landscaping as decorative 'lava rock,' in gas grills to distribute heat, as high-temperature insulation, and as an aggregate in lightweight concrete for construction.

Geological facts

Scoria is often confused with pumice, but scoria is denser, has larger bubbles, and generally sinks in water, whereas pumice is light enough to float. It frequently forms the bulk of cinder cone volcanoes.

Field identification & locations

Identify in the field by its sponge-like appearance, lightweight feel compared to solid rock, and sharp, abrasive surface. Found near volcanic vents and cinder cones globally, particularly in Iceland, the Canary Islands, and the Western USA.

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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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Blue Apatite

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

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Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

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Magnetite

Magnetite (Fe3O4)

mineral