igneous

Basalt with Vesicles

Vesicular Basalt

Hardness: 5-6 (Mohs scale); Color: Dark grey to black or brownish-red; Luster: Dull/Earthy; Structure: Fine-grained (aphanitic) with small pits or cavities (vesicles); Density: High.

Hardness: 5-6 (Mohs scale)
Color: Dark grey to black or brownish-red
Luster: Dull/Earthy

Identified April 1, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs scale); Color: Dark grey to black or brownish-red; Luster: Dull/Earthy; Structure: Fine-grained (aphanitic) with small pits or cavities (vesicles); Density: High.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The pits (vesicles) are created by gas bubbles that were trapped in the lava as it solidified.

Uses & applications

Used in construction as road base, concrete aggregate, and railroad ballast. Larger decorative pieces are used in landscaping and aquariums.

Geological facts

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

Field identification & locations

Identify in the field by its dark color, heavy weight for its size, and the presence of small holes or pits on the surface. Commonly found near volcanic sites or in glacial till.

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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