igneous

Scoria (Lava Rock)

Vesicular Basalt / Scoria

Hardness: 5-6 Mohs scale; Color: Dark red, brown, black, or dark grey; Luster: Dull/Earthy; Structure: Vesicular (highly porous/pitted); Specific gravity: 2.0-3.0 (dense enough to sink in water, unlike pumice).

Hardness: 5-6 Mohs scale
Color: Dark red, brown, black, or dark grey
Luster: Dull/Earthy

Identified March 30, 2026More igneous →

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Physical properties

Formation & geological history

Formed from extrusive volcanic eruptions where gas bubbles are trapped as the lava cools rapidly. It is typically mafic/basaltic in composition. Found in volcanic regions ranging from prehistoric eras to modern eruptions.

Uses & applications

Used extensively in landscaping, gas grills, high-temperature insulation, drainage systems, and as an abrasive in concrete or road construction.

Geological facts

Scoria is often confused with pumice, but it is much heavier and darker because it contains more iron and magnesium. Its holes - called vesicles - are the result of volcanic gasses expanding as the lava reached the surface.

Field identification & locations

Identify by its 'swiss cheese' appearance, rough texture, and dark color. It feels lightweight for its size but will not float in water. Commonly found near cinder cones and volcanic fields in places like the American Southwest, Iceland, and Hawaii.

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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