igneous

Scoria (with Iron Oxidation)

Vesicular Basalt / Scoria

Hardness: 5-6 Mohs. Color: Black to dark gray base with reddish-brown to orange oxidation. Luster: Dull to sub-metallic. Structure: Highly vesicular (honeycombed). Specific Gravity: 2.5-3.0 (though it feels light due to air pockets).

Hardness: 5-6 Mohs
Luster: Dull to sub-metallic

Identified January 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of gas-rich mafic magma (lava) ejected during explosive volcanic eruptions. The holes (vesicles) are created by trapped gas bubbles. Common in Cenozoic volcanic fields.

Uses & applications

Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, lightweight concrete aggregate, and as a traction aid on icy roads.

Geological facts

Red scoria gets its color from the oxidation of iron-rich minerals (like olivine or pyroxene) while the rock is still hot or through subsequent weathering, turning magnetite/ilmenite into hematite or limonite.

Field identification & locations

Identify by its 'sponge-like' appearance and dark color. Unlike pumice, scoria typically sinks in water. Found near cinder cones and volcanic vents in regions like Iceland, Hawaii, and the Western United States.

Other igneous specimens

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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