igneous

Vesicular Basalt (or Porphyritic Scoria)

Vesicular Basalt

Hardness: 5-6 (Mohs scale); Color: Light grey to dark grey/reddish with dark phenocrysts; Luster: Dull/Earthy; Structure: Amorphous/Fine-grained with numerous gas holes (vesicles); Specific Gravity: 2.7-3.3

Hardness: 5-6 (Mohs scale)
Color: Light grey to dark grey/reddish with dark phenocrysts
Luster: Dull/Earthy

Identified April 4, 2026More igneous →

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Physical properties

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. They are found in volcanic regions of all ages, from recent eruptions to ancient tectonic sites.

Uses & applications

Used in landscaping, as a lightweight aggregate in concrete, for insulation, or as a decorative stone in aquariums. Can be used as an abrasive (pumice-like) depending on density.

Geological facts

Vesicular rocks like this are often light enough to float if they have a high enough gas-to-rock ratio (though basalt usually sinks). The dark spots in this specific specimen appear to be mineral 'phenocrysts' or secondary mineral infills (amygdules).

Field identification & locations

Identify in the field by its 'pock-marked' appearance and relatively heavy weight compared to pumice. Often found near shield volcanoes or Rift Valley formations.

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