igneous

Vesicular Basalt

Extrusive mafic igneous rock (primarily Plagioclase Feldspar and Pyroxene)

Hardness: 6 (Mohs scale); Color: Dark gray to reddish-brown (weathered); Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8 - 3.0

Hardness: 6 (Mohs scale)
Color: Dark gray to reddish-brown (weathered)
Luster: Dull/Earthy

Identified March 29, 2026More igneous →

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Physical properties

Hardness: 6 (Mohs scale); Color: Dark gray to reddish-brown (weathered); Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8 - 3.0

Formation & geological history

Formed from the rapid cooling of magnesium and iron-rich lava at the Earth's surface. The pits (vesicles) are created by gas bubbles trapped in the cooling magma. Ages range from modern flows to billions of years old.

Uses & applications

Used in construction as road base, railroad ballast, and concrete aggregate. Highly porous specimens are used in landscaping, gas grills, and aquarium filtration.

Geological facts

Basalt is the most common rock type in the 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 by its heavy weight (density) for its size, dark interior, and distinctive 'Swiss cheese' texture. Commonly found in volcanic fields like the Pacific Northwest, Hawaii, or Iceland.

Other igneous specimens

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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

mineral

Blue Apatite

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

mineral

Magnetite

Magnetite (Fe3O4)

mineral