igneous

Lava Rock (Scoria)

Scoria (Mafic volcanic rock)

Hardness: 5-6 Mohs; Color: Black, dark gray, dark brown, or reddish-brown; Luster: Dull or submetallic; Structure: Highly vesicular/porous; Cleavage: None; Specific Gravity: varies (low due to air pockets)

Hardness: 5-6 Mohs
Color: Black, dark gray, dark brown, or reddish-brown
Luster: Dull or submetallic

Identified May 24, 2026More igneous →

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Physical properties

Formation & geological history

Formed from gas-rich, mafic magma cooling rapidly near the surface of a volcano. The holes (vesicles) are formed by trapped gas bubbles that expand as the pressure drops during eruption.

Uses & applications

Used widely in landscaping, gas grills, aquarium filtration, hot stone massages, and as an additive in lightweight concrete.

Geological facts

Scoria is different from pumice because scoria is mafic (dark-colored) and denser, whereas pumice is felsic and often floats on water. Most lava rocks are found in young volcanic fields.

Field identification & locations

Identify by its dark color, lightweight feel compared to solid basalt, and numerous visible holes or vesicles. Commonly found in volcanic regions like Iceland, Hawaii, and the Western US.

Other igneous specimens

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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