igneous

Scoria (Lava Rock)

Vesicular Basalt / Scoria

Hardness: 5.0-6.0 (Mohs scale), Color: Dark gray to black (occasionally reddish-brown), Luster: Dull/Sub-metallic, Structure: Highly vesicular (porous/bubbly), Specific Gravity: Low (often floats briefly in water due to trapped air).

Hardness: 5

Identified March 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of mafic lava rich in dissolved gases. As the magma erupts, gases expand and escape, leaving behind a frozen 'foam' of rock. Common in Cenozoic volcanic regions.

Uses & applications

Used in landscaping (lava rock), gas grills for heat retention, lightweight concrete, high-temperature insulation, and as an abrasive in stone-washing textiles.

Geological facts

Scoria is often mistaken for pumice; however, scoria has larger vesicles and thicker cell walls, making it denser and darker in color than pumice.

Field identification & locations

Identify in the field by its sponge-like appearance and lighter-than-expected weight for its size. Commonly found near cinder cones and basaltic volcanic vents (e.g., Iceland, Hawaii, Craters of the Moon NM).

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