igneous

Lava Rock (Scoria)

Scoria (Basaltic Scoria)

Hardness: 5-6 (Mohs), Color: Dark brown to black or reddish-brown, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained) with vesicular texture, SG: 0.8-2.1 (often floats on water briefly)

Identified May 25, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs), Color: Dark brown to black or reddish-brown, Luster: Dull/Earthy, Crystal Structure: Aphanitic (fine-grained) with vesicular texture, SG: 0.8-2.1 (often floats on water briefly)

Formation & geological history

Formed from the rapid cooling of gas-rich basaltic lava. These vesicles are created as gases expand and become trapped within the solidifying rock during volcanic eruptions.

Uses & applications

Used in landscaping, gas grills, high-temperature insulation, drainage systems, and as an abrasive in stone-washing textiles.

Geological facts

Scoria is different from pumice in that it has larger vesicles and thicker cell walls, making it denser and darker. It often forms the main component of cinder cones.

Field identification & locations

Identify by its highly vesicular (porous) surface, lightweight feel, and sub-metallic to dull dark colors. Commonly found near dormant or active volcanic sites.

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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