igneous

Scoria (Lava Rock)

Scoria

Hardness: 5-6 (variable); Color: Dark brown, black, or reddish; Luster: Dull to submetallic; Structure: Vesicular (highly porous/holed); Cleavage: None; Specific Gravity: 2.0-3.0 (low for a rock due to air pockets).

Hardness: 5-6 (variable)
Color: Dark brown, black, or reddish
Luster: Dull to submetallic

Identified May 9, 2026More igneous →

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Physical properties

Formation & geological history

Formed through volcanic activity where gas is trapped in cooling basaltic or andesitic magma, creating a vesicular texture. It is typical of relatively recent geological ages (Holocene/Pleistocene), appearing near volcanic vents.

Uses & applications

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

Geological facts

Scoria is often mistaken for pumice, but it is denser and has larger vesicles with thicker walls. Unlike pumice, scoria is too heavy to float in water.

Field identification & locations

Identify by its dark color and 'sponge-like' appearance with many visible holes. It is commonly found in volcanic fields such as those in Iceland, Hawaii, and the Canary Islands. Collectors search for specimens with unique colors or large vesicles.

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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