Ammolite is one of the rarest gems on Earth, and it started life as a sea creature. It is the fossilised shell of ammonites, coiled molluscs that swam the oceans over 70 million years ago. The shell's aragonite layers were preserved and compressed, and now they flash brilliant reds, greens and blues like an opal. Gem-quality ammolite comes from just one region, along the Bearpaw Formation in Alberta, Canada. The Blackfoot people knew it long before jewellers did and called it the buffalo stone.
Ammolite is soft, around 3.5 to 4.5 on the Mohs scale, and the colourful layer is naturally thin and prone to flaking. For that reason, most jewellery pieces are sold as doublets or triplets, where the gem layer is backed with stone and capped with clear quartz or spinel. That is normal, disclosed practice and it makes the gem far more wearable. Pendants and earrings suit it best. Keep it away from knocks, chemicals and ultrasonic cleaners, and wipe it with a soft, damp cloth.
Opal and labradorite share a similar shifting rainbow flash, and petrified wood is also a fossil-turned-gem.
