igneous

Vesicular Basalt (or Scoria)

Basalt (Aphanitic-Vesicular Mafic Igneous Rock)

Hardness: 5-6 (Mohs scale); Color: charcoal black to dark grey; Luster: dull to vitreous; Structure: vesicular (porous) with many small holes called vesicles; Composition: rich in magnesium and iron (mafic).

Hardness: 5-6 (Mohs scale)
Color: charcoal black to dark grey
Luster: dull to vitreous

Identified May 10, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of basaltic lava at or near the surface. The holes (vesicles) are created by gas bubbles trapped during solidification. Often dates from the Cenozoic era to recent volcanic events.

Uses & applications

Used in landscaping (lava rock), construction as an aggregate in concrete or asphalt, road base, and as ground cover for heat retention in gardening.

Geological facts

Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.

Field identification & locations

Identify by its dark color, heavy weight (relative to its appearance), and the distinctive Swiss-cheese-like holes. Found globally in volcanic fields like those in Hawaii, Iceland, and the Pacific Northwest.

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