igneous

Vesicular Basalt (Scoria)

Vesicular Basalt

Hardness: 5-6 (Mohs); Color: Dark brown, black, or reddish-brown; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained) with many vesicles (gas holes); Specific Gravity: 2.2-2.7

Hardness: 5-6 (Mohs)
Color: Dark brown, black, or reddish-brown
Luster: Dull/earthy

Identified May 17, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs); Color: Dark brown, black, or reddish-brown; Luster: Dull/earthy; Crystal Structure: Aphanitic (fine-grained) with many vesicles (gas holes); Specific Gravity: 2.2-2.7

Formation & geological history

Formed from rapid cooling of gas-rich basaltic lava at the Earth's surface. The holes (vesicles) are created by trapped gas bubbles that escaped as the rock solidified. Common in volcanic regions.

Uses & applications

Used in landscaping for volcanic rock features, as road base, for gas grills (lava rocks), and sometimes in cement production.

Geological facts

Scoria is similar to pumice but is more dense and darker in color; unlike pumice, most scoria will sink in water because its vesicles are larger and less interconnected.

Field identification & locations

Identify by its 'Swiss cheese' appearance with many holes and its relatively light weight compared to solid basalt. Often found near cinder cones and shield volcanoes.

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