igneous

Scoria (with likely iron oxidation)

Scoria (Basaltic Scoria)

Hardness: 5-6 (Mohs). Color: Dark brown, reddish-brown, or black. Luster: Dull to submetallic. Crystal structure: Aphanitic (fine-grained) with high vesicularity (small holes/voids). Specific gravity: 2.0-3.0.

Hardness: 5-6 (Mohs)
Color: Dark brown, reddish-brown, or black
Luster: Dull to submetallic

Identified May 13, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich basaltic or andesitic magma. As the lava is erupted, dissolved gases expand into bubbles (vesicles) which are frozen into the rock as it quickly solidifies. Common in volcanic cinder cones.

Uses & applications

Used in landscaping (lava rock), gas grills, high-temperature insulation, drainage stones, and lightweight concrete aggregates.

Geological facts

Scoria is often mistaken for pumice; however, scoria has larger vesicles, thicker walls between vesicles, and is dense enough to sink in water, whereas pumice often floats.

Field identification & locations

Identify by its highly vesicular (bubbly) texture and dark color. It feels relatively lightweight for its size but is heavier than pumice. Common in volcanic regions such as the Western US, Iceland, and Italy.

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