igneous

Vesicular Basalt (Scoria)

Vesicular Basalt

Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) with vesicles (gas bubbles); Specific gravity: 2.8-3.0.

Hardness: 5-6 (Mohs)
Color: dark gray, black, or reddish-brown
Luster: dull to earthy

Identified May 21, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) with vesicles (gas bubbles); Specific gravity: 2.8-3.0.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) are created by trapped gas bubbles that escaped as the lava solidified near the surface of a volcano.

Uses & applications

Used in landscaping, high-temperature insulation, drainage rock, gas grill 'lava rocks', and as an abrasive in stone-washing processes.

Geological facts

Scoria is often mistaken for pumice; however, basaltic scoria is denser and will usually sink in water, whereas pumice floats. It is common on the surfaces of shield volcanoes.

Field identification & locations

Identify by its 'Swiss cheese' texture and dark color. Common in volcanic regions like Hawaii, Iceland, and the Pacific Northwest. Look for lightweight (relative to solid rock) vesicular textures.

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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