igneous

Vesicular Basalt

Extrusive mafic igneous rock (primarily Plagioclase feldspar and Pyroxene)

Hardness: 6-7 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained) with visible gas bubbles (vesicles); Specific Gravity: 2.8-3.0.

Hardness: 6-7 on Mohs scale
Color: Dark grey to black
Luster: Dull/earthy

Identified March 18, 2026More igneous →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Dark grey to black; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained) with visible gas bubbles (vesicles); Specific Gravity: 2.8-3.0.

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The holes (vesicles) are created by gas bubbles that were trapped in the lava as it solidified. Geological age varies from Pre-Cambrian to modern volcanic eruptions.

Uses & applications

Used extensively in construction as aggregate for road base and concrete, as decorative landscaping stone (lava rock), and sometimes as an abrasive (scoria) in industrial stone-washing for textiles.

Geological facts

Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Large-scale basaltic lava flows can form unique geometric columns, such as those at the Giant's Causeway in Ireland.

Field identification & locations

Identify in the field by its dark color, heavy weight (relative to size), and characteristic 'pock-marked' or holey surface. Common in volcanic regions such as Iceland, Hawaii, and the Pacific Northwest of the USA.

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