igneous

Scoria (Vesicular Basalt)

Scoria (Extrusive Igneous Rock)

Hardness: 5-6 (Mohs scale), Color: Dark red, reddish-brown, or black (oxidized in this specimen), Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained) with high vesicularity (pitted with gas bubbles), Specific Gravity: 0.8 to 2.1 (often floats on water briefly but usually sinks).

Identified April 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed from cinder cone volcanic eruptions where gas is trapped in cooling lava. The reddish color indicates the oxidation of iron-rich minerals (magnetite or olivine) within the basaltic magma as it cooled in an oxygen-rich environment.

Uses & applications

Used in landscaping (lava rock), gas grill briquettes, high-temperature insulation, drainage stones, and lightweight concrete aggregate.

Geological facts

Scoria is often mistaken for pumice, but scoria has larger vesicles, thicker walls, and is denser. The deep red color is a result of iron rusting inside the rock during or after the eruption.

Field identification & locations

Identify in the field by its very lightweight, 'sponge-like' appearance and numerous holes (vesicles). It is commonly found around volcanic vents and cinder cones, such as those in the Western United States or Iceland.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

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)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral