igneous

Vesicular Basalt

Basalt (principally Plagioclase and Pyroxene)

Hardness: 6-7 on Mohs scale; Color: Dark grey to black, often weathering to brown/red; Luster: Dull to earthy; Texture: Vesicular (contains small cavities or gas bubbles); Crystal structure: Aphanitic (fine-grained).

Hardness: 6-7 on Mohs scale
Color: Dark grey to black, often weathering to brown/red
Luster: Dull to earthy

Identified April 3, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. The vesicles are formed by gas bubbles that were trapped in the lava as it cooled.

Uses & applications

Used in construction as aggregate, for road base, concrete, and railroad ballast. Larger decorative pieces are used in landscaping and as 'lava rocks' for grills.

Geological facts

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

Field identification & locations

Identify in the field by its dark color, heavy weight relative to size (high density), and the presence of small holes (vesicles). Found in volcanic regions such as the Pacific Northwest or Hawaii.

Other igneous specimens

See all

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