Rocksday

Aragonite

Same chemistry as calcite, different crystal structure. It builds pearls and seashells and forms spiky 'sputnik' clusters.

Aragonite specimen
Photo: JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0, via Wikimedia Commons

How to identify aragonite

  • Fizzes in acid.
  • Needle-like or six-sided twinned crystals.
  • No rhomb cleavage, unlike calcite.
  • Slightly heavier than calcite.

Often confused with

Where it's found

  • Molina de Aragón, Spain
  • Morocco
  • Carlsbad Caverns, New Mexico

Uses

Pearls and mother-of-pearl are made of it.

Rock tumbling

Can be tumbled with care.

Did you know?

It's named after Aragón in Spain, where its six-sided twin crystals were first described.

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