igneous

Scoria (Lava Rock)

Scoria

Hardness: 5.0 - 6.0; Color: Dark red to reddish-brown (due to iron oxidation); Luster: Dull to sub-vitreous; Structure: Vesicular (highly porous/holey); Specific Gravity: 0.8 - 2.1 (low, but usually sinks in water contrast to pumice).

Hardness: 5
Color: Dark red to reddish-brown (due to iron oxidation)
Luster: Dull to sub-vitreous

Identified May 7, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from extrusive volcanic activity during explosive eruptions. Gasses trapped in cooling basaltic or andesitic magma create bubbles (vesicles) as the pressure drops suddenly upon surfacing.

Uses & applications

Commonly used in landscaping as decorative ground cover, in gas grills as 'lava rocks' for heat retention, in high-temperature insulation, and as lightweight aggregate for concrete.

Geological facts

Unlike its cousin pumice, scoria typically has larger holes and thicker walls, making it dense enough to sink in water. The red color is usually a result of the oxidation of iron within the lava while it is still hot.

Field identification & locations

Identify in the field by its sponge-like, porous appearance and relatively light weight despite being rock. Found near cinder cones and volcanic vents worldwide, particularly in Hawaii, Iceland, and the Canary Islands.

Other igneous specimens

See all

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