igneous

Vesicular Basalt (Scoria)

Vesicular Basalt

Hardness: 5-6 Mohs. Color: Dark gray, black, or reddish-brown with green olivine inclusions. Luster: Dull to earthy. Structure: Vesicular (pitted with gas bubbles). Cleavage: None. Specific gravity: 2.8-3.0.

Hardness: 5-6 Mohs
Luster: Dull to earthy

Identified May 19, 2026More igneous →

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Physical properties

Formation & geological history

Formed from rapid cooling of mafic lava rich in dissolved gases. As the lava depressurizes upon erupting, gas bubbles (vesicles) are trapped as the rock solidifies. Common in volcanic fields of various geological ages.

Uses & applications

Used in landscaping, high-temperature insulation, gas grill stones, drainage systems, and as an abrasive in stone-washing processes. Small specimens are collected for educational purposes.

Geological facts

The holes in this rock, called vesicles, are actually prehistoric gas bubbles. If the bubbles are large and numerous enough, the rock can become lightweight, though unlike pumice, basaltic scoria usually sinks in water.

Field identification & locations

Identify by its dark color, heavy weight compared to pumice, and the presence of small circular cavities. Often found near cinder cones or basaltic lava flows. Green tints usually indicate the presence of olivine.

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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