igneous

Scoria

Vesicular Basalt / Scoria

Hardness: 5-6 (Mohs scale); Color: Dark brown, black, or reddish; Luster: Dull (earthy); Crystal structure: Aphanitic (fine-grained) with large vesicles; Specific gravity: 2.5-3.0 (though it often feels lighter due to air pockets).

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

Identified March 17, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich basaltic magma cooling rapidly during a volcanic eruption. As the pressure drops, dissolved gases expand into bubbles which are trapped as the lava solidifies, creating a 'vesicular' texture.

Uses & applications

Used in high-temperature insulation, lightweight concrete, landscaping (lava rock), drainage stone, and as an abrasive in 'stone-washed' jeans.

Geological facts

Scoria is different from pumice in that it has larger vesicles and thicker cell walls, making it dense enough to sink in water, whereas pumice often floats.

Field identification & locations

Identify by its dark color, high porosity with visible rounded holes, and relatively heavy feel compared to pumice. Common in volcanic fields like those in Iceland, Hawaii, and the Western US.

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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