Porcellanite

Porcellanite worked into Neolithic axes, Northern Ireland

Porcellanite or porcelanite, is a hard, dense rock somewhat similar in appearance to unglazed porcelain. It is often an impure variety of chert containing clay and calcareous matter.[1]

At Tievebulliagh, Northern Ireland, porcellanite is a tough contact metamorphosed hornfels formed from a lateritic soil horizon within a basaltic intrusive/extrusive sequence. It is the site of a Neolithic axe or stone tool quarry.[2]

References

Wikimedia Commons has media related to Porcellanite.
  1. Porcellanite, Encyclopædia Britannica Premium Service
  2. Tievebulliagh
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