igneous

Scoria (Lava Rock)

Vesicular Basalt / Scoria

Hardness: 5-6 Mohs. Color: Dark brown, black, or reddish-purple. Luster: Dull/Sub-metallic. Structure: Vesicular (full of small bubbles or cavities). Specific Gravity: 2.5–3.0 (though it often feels lighter due to air pockets).

Hardness: 5-6 Mohs
Color: Dark brown, black, or reddish-purple
Luster: Dull/Sub-metallic

Identified March 23, 2026More igneous →

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Physical properties

Formation & geological history

Formed from volcanic eruptions where gas-rich magma cools rapidly, trapping bubbles (vesicles) as it solidifies. Can be found in volcanic fields of any age, typically associated with cinder cones.

Uses & applications

Used widely in landscaping (lava rock), high-temperature insulation, gas barbecue grills for heat distribution, lightweight aggregate in concrete, and road construction for traction.

Geological facts

Unlike pumice, scoria has a density greater than water and will sink rather than float. It is essentially the 'cinder' found in cinder cone volcanoes.

Field identification & locations

Identify by its highly pitted (Swiss cheese) texture and dark color. Common in volcanic regions like Iceland, Hawaii, and the Western United States. Collectors should look for unique glass-like cooling or distinct color variations.

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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