igneous

Scoria

Vesicular Basalt / Scoria

Hardness: 5-6 (Mohs). Color: Black, dark gray, reddish-brown. Luster: Dull/Glassy. Structure: Vesicular (bubble-like holes). Specific Gravity: 2.5-3.0 (though it feels light due to air pockets).

Hardness: 5-6 (Mohs)
Color: Black, dark gray, reddish-brown
Luster: Dull/Glassy

Identified January 5, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs). Color: Black, dark gray, reddish-brown. Luster: Dull/Glassy. Structure: Vesicular (bubble-like holes). Specific Gravity: 2.5-3.0 (though it feels light due to air pockets).

Formation & geological history

Formed from gas-rich mafic magma (basaltic) that is ejected from a volcano. As the lava solidifies rapidly, gas bubbles are trapped, creating a porous texture. Typically found in cinder cones.

Uses & applications

Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, drainage stones, and as a lightweight aggregate in concrete blocks.

Geological facts

Scoria is different from Pumice; Scoria has larger vesicles, thicker walls, and is denser, meaning it usually sinks in water while pumice floats.

Field identification & locations

Identify by its dark color (black or red), rough sandpaper-like texture, and many small visible holes (vesicles). Commonly found near volcanic sites like Craters of the Moon or Hawaiian volcanic fields.

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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