igneous

Scoria (Vesicular Basalt)

Scoria (Extrusive Mafic Igneous Rock)

Hardness: 5-6 (Mohs scale), Color: Black to dark gray, Luster: Dull/Sub-metallic, Structure: Vesicular (porous), Cleavage: None, Specific Gravity: 2.5-3.0 but often floats temporarily due to trapped air.

Identified April 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of gas-rich mafic lava (basaltic) ejected from a volcano. The holes (vesicles) are created by gas bubbles that were trapped as the lava solidified. Primarily associated with Cenozoic to recent volcanic activity.

Uses & applications

Used widely in landscaping, gas grill lava rocks, drainage systems, high-temperature insulation, and as a lightweight aggregate in concrete.

Geological facts

Scoria differs from pumice because it is mafic and has thicker vesicle walls, making it denser and darker. Massive deposits often form 'cinder cones' around volcanic vents.

Field identification & locations

Identify by its dark color, heavy vesicular texture (looking like a sponge), and rough, abrasive surface. Commonly found in volcanic regions like Hawaii, Iceland, and the Western United States.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Magnetite

Magnetite (Fe3O4)

mineral