igneous

Scoria (Vesicular Basalt)

Scoria (Extrusive Igneous Rock)

Hardness: 5-6 (Mohs scale); Color: Dark brown, black, or reddish-brown; Luster: Sub-metallic to dull; Structure: Highly vesicular (honeycombed with gas bubbles); Specific Gravity: 0.8 to 2.1 (often sink in water, unlike pumice); Composition: Mainly plagioclase feldspar, pyroxene, and olivine.

Hardness: 5-6 (Mohs scale)
Color: Dark brown, black, or reddish-brown
Luster: Sub-metallic to dull

Identified March 20, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of basaltic or andesitic lava containing high amounts of dissolved gases. As the lava erupts, gases expand and create bubbles (vesicles) that are frozen in place as the rock solidifies. Most scoria dates from the Cenozoic era to recent volcanic activity.

Uses & applications

Used in landscaping as decorative 'lava rock', in gas grills to retain heat, as high-temperature insulation, in lightweight concrete, and for drainage in horticultural applications.

Geological facts

Scoria is often confused with pumice, but scoria has larger vesicles, thicker walls between bubbles, and is denser (pumice usually floats in water, while scoria usually sinks). Large deposits are often found in cinder cones.

Field identification & locations

Identify by its 'swiss cheese' appearance, dark color, and rough, abrasive texture. Commonly found near volcanic vents and cinder cones in places like the American Southwest, Iceland, Italy, and Hawaii.

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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)

mineral

Magnetite

Magnetite (Fe3O4)

mineral