Rocksday

Gneiss

A high-grade metamorphic rock with bold light and dark bands, formed under intense heat and pressure.

Gneiss specimen
Photo: No machine-readable author provided. Siim assumed (based on copyright claims)., CC BY-SA 3.0, via Wikimedia Commons

How to identify gneiss

  • Alternating light and dark bands, often wavy.
  • Coarse, visible grains.
  • Hard; doesn't split into sheets.
  • Bands may be folded.

Often confused with

Where it's found

  • Acasta River, Canada
  • Outer Hebrides, Scotland
  • Adirondacks, New York

Uses

Building stone and countertops.

Rock tumbling

Great for tumbling.

Did you know?

Canada's Acasta Gneiss is about 4 billion years old — among the oldest rocks on Earth.

Think you could spot it from a blurry close-up?

Play today's Rocksday