igneous

Scoria (Lava Rock)

Scoria (Vesicular Basaltic Glass/Rock)

Hardness: 5-6 Mohs. Color: Reddish-brown to dark brown/black. Luster: Dull/Earthy. Structure: Highly vesicular (honeycombed with gas bubbles). Cleavage: None. Specific Gravity: Typically low due to air pockets, sometimes floats on water temporarily.

Hardness: 5-6 Mohs
Color: Reddish-brown to dark brown/black
Luster: Dull/Earthy

Identified April 6, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich basaltic magma cooling rapidly during a volcanic eruption (extrusive igneous). The gas bubbles are trapped as the lava solidifies, creating the porous texture. Common in Cenozoic volcanic fields.

Uses & applications

Used widely in landscaping (lava rock), as high-temperature insulation, in gas grills to distribute heat, and sometimes as a lightweight aggregate for concrete or as a drainage material.

Geological facts

Scoria is often confused with pumice; however, scoria has thicker vesicle walls and is denser, usually sinking in water, whereas pumice often floats. The red color is typically due to the oxidation of iron within the lava.

Field identification & locations

Identify in the field by its very high porosity, rough abrasive texture, and dark red or black color. Found near cinder cones and volcanic craters globally, such as in the Western US, Iceland, and Italy.

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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