igneous

Basalt with Scoria/Vesicular texture

Vesicular Basalt (primarily Plagioclase feldspar, Pyroxene, and Olivine)

Hardness: 5-6 (Mohs scale); Color: Dark grey to black, often weathering to reddish-brown (as seen in image) due to iron oxidation; Luster: Dull/Earthy; Structure: Aphanitic with vesicles (gas bubbles); Specific Gravity: 2.8–3.0.

Hardness: 5-6 (Mohs scale)
Luster: Dull/Earthy

Identified March 17, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava (mafic) at the Earth's surface during volcanic eruptions. The holes (vesicles) are created by trapped gas bubbles that escaped as the lava solidified. They can range from recent to billions of years old.

Uses & applications

Commonly used in construction as aggregate for roads, railroad ballast, and concrete. Highly vesicular varieties (Scoria) are used in landscaping, gas grills, and as abrasive polishing stones.

Geological facts

Basalt is the most common rock type in the Earth's crust as it makes up most of the ocean floor. It is also found on the Moon and Mars, where large basaltic plains are known as 'maria'.

Field identification & locations

Identify in the field by its weight (relatively heavy for its size), dark interior when broken, and the presence of small spherical or oval pits. It is found in volcanic regions worldwide, such as the Pacific Northwest (USA), Iceland, and Hawaii.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

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Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral