igneous

Vesicular Basalt

Extrusive Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)

Hardness: 5-6 (Mohs scale); Color: Dark grey to dull brown; Luster: Dull/Earthy; Structure: Vesicular (contains many small gas bubbles or pits); Specific Gravity: 2.8 - 3.0

Hardness: 5-6 (Mohs scale)
Color: Dark grey to dull brown
Luster: Dull/Earthy

Identified April 10, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs scale); Color: Dark grey to dull brown; Luster: Dull/Earthy; Structure: Vesicular (contains many small gas bubbles or pits); Specific Gravity: 2.8 - 3.0

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The 'pits' or vesicles are formed by trapped gas bubbles that escaped as the lava solidified.

Uses & applications

Used primarily in construction (aggregate), road base, and as decorative landscaping stones (lava rocks). High-quality vesicular basalt is also used for 'hot stone' massage therapy due to heat retention.

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 (relative to size), dark color, and characteristic 'pitted' surface. Commonly found in volcanic regions, riverbeds near volcanic ranges, and coastal areas.

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