Rocksday

Blueschist

A rare blue-gray rock formed at high pressure but low temperature in subduction zones.

Blueschist specimen
Photo: Shannon Heinle, CC0, via Wikimedia Commons

How to identify blueschist

  • Lavender to blue-gray color.
  • Foliated, sometimes with red garnets.
  • Found in old subduction zones.

Often confused with

Where it's found

  • Franciscan Complex, California
  • Syros, Greece
  • Western Alps

Uses

Scientific study of subduction.

Rock tumbling

Can be tumbled with care.

Did you know?

Its blue comes from the amphibole mineral glaucophane.

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

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