igneous

Scoria

Vesicular Basaltic Glass

Hardness: 5-6 (Mohs scale); Color: dark red, brown, or black; Luster: dull to vitreous; Structure: vesicular (porous); Specific gravity: 0.8-2.1 (some float on water briefly, but most sink).

Hardness: 5-6 (Mohs scale)
Color: dark red, brown, or black
Luster: dull to vitreous

Identified March 31, 2026More igneous →

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Physical properties

Hardness: 5-6 (Mohs scale); Color: dark red, brown, or black; Luster: dull to vitreous; Structure: vesicular (porous); Specific gravity: 0.8-2.1 (some float on water briefly, but most sink).

Formation & geological history

Formed from the rapid cooling of basaltic or andesitic magma containing high levels of dissolved gases which expand to create holes (vesicles). Commonly found in cinder cones and volcanic fields.

Uses & applications

Used extensively in landscaping, drainage systems, gas grills for heat retention, lightweight concrete manufacturing, and as abrasive traction for icy roads.

Geological facts

Scoria is often confused with pumice, but it is denser and has larger vesicles; it is the primary material that makes up cinder cone volcanoes.

Field identification & locations

Identify by its rough, sponge-like texture, dark color, and lightness relative to solid basalt. Commonly found in volcanic regions like Hawaii, Italy (Mount Etna), and the American Southwest.

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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