Igneous

Scoria

Scoria (Vesicular Basaltic Glass)

Hardness: 5-6 Mohs. Color: Dark brown, black, or reddish-black. Luster: Dull to sub-metallic. Crystal Structure: Aphanitic (fine-grained) to glassy. Cleavage: None. Specific Gravity: 0.8-2.1. Notable for a highly vesicular (bubbly) texture with numerous large pits.

Hardness: 5-6 Mohs
Color: Dark brown, black, or reddish-black
Luster: Dull to sub-metallic

Identified March 15, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of gas-rich basaltic lava ejected from a volcano. The gas bubbles (vesicles) are trapped as the lava solidifies. They are common in cinder cones and volcanic fields of the Cenozoic era to modern times.

Uses & applications

Used widely in landscaping, gas grill lava rocks, high-temperature insulation, drainage rock, and as an abrasive in stone-washed denim production. It is also used in lightweight concrete and road construction.

Geological facts

Scoria is often confused with pumice; however, scoria has thicker vesicle walls and is denser, which usually causes it to sink in water, whereas pumice often floats. It is a primary component of volcanic cinder cones.

Field identification & locations

Identify in the field by its very lightweight, porous, 'sponge-like' appearance and dark color. It is commonly found in volcanic regions like Hawaii, Iceland, the Canary Islands, and the Western United States (Craters of the Moon, Idaho).

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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