Scoria is an igneous volcanic rock, specifically a dark, mafic, highly vesicular pyroclastic rock that forms when gas‑rich lava froths and solidifies during an eruption.

Rock type in simple terms

  • Scoria is an extrusive igneous rock, meaning it cools and solidifies from lava at or near Earth’s surface.
  • It is also described as a pyroclastic rock because it forms from volcanic fragments and blobs of lava that are ejected during eruptions.

Key features of scoria

  • Texture: Highly vesicular, with many gas bubble holes, giving it a rough, sponge‑like surface.
  • Composition: Usually mafic (basaltic), rich in iron and magnesium, and often largely volcanic glass with some crystals like plagioclase, pyroxene, and olivine.
  • Color: Commonly dark—black, dark brown, or reddish‑brown, like the “lava rock” sold for grills and landscaping.

Quick Scoop (forum‑style)

When people ask “what type of rock is scoria,” geologists would answer:
“It’s a mafic, vesicular, extrusive igneous rock—basically a bubbly basaltic lava chunk from explosive eruptions.”

  • Scoria is denser and usually darker than pumice, so it often sinks in water, unlike pumice which tends to float.
  • Around volcanoes, these pieces are also called cinders, which is why small scoria fragments build “cinder cones.”

Information gathered from public forums or data available on the internet and portrayed here.