igneous

Scoria

Vesicular Basalt / Scoria

Hardness: 5-6 (Mohs scale); Color: Dark reddish-brown to black; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: Low (often floats briefly on water due to vesicles).

Hardness: 5-6 (Mohs scale)
Color: Dark reddish-brown to black
Luster: Dull/Earthy

Identified March 22, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of gas-rich basaltic lava during volcanic eruptions. The holes (vesicles) are created by trapped gas bubbles that expand as pressure drops during the eruption.

Uses & applications

Used extensively in landscaping, gas grill lava rocks, high-temperature insulation, concrete aggregate, and as a drainage material in horticulture.

Geological facts

Scoria differs from pumice in that it has larger vesicles and thicker cell walls, making it denser and darker. Massive deposits are often found in cinder cones around volcanic vents.

Field identification & locations

Identify by its 'Swiss cheese' appearance, lightweight nature, and rough, abrasive texture. Commonly found in volcanic regions like the American Southwest, Iceland, and Italy.

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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