Ammolite is an organic gemstone made of aragonite (CaCO3), the same mineral that forms pearls. For a gemstone to be classified as 'organic' it must have been formed by a plant or animal. Examples of other organic gemstones are pearls and amber.
Ammolite is the multi-coloured iridescent outer layer of a fossil, ammonite. An ammonite is an ancient variety of squid that was abundant during the time the dinosaurs roamed the earth. They became extinct near the end of the Cretaceous period, 65 million years ago. Ammolite occurs in association with two species of fossil ammonites: Placenticeras meeki and Placenticeras intercalare. The ammonites were preserved in a sediment layer in the Rocky Mountains, called the BearPaw formation, and ammolite was formed from intense heat and compaction over a period of approximately seventy million years.
Ammolite is very rare and the only gem quality deposit is concentrated near Lethbridge, Alberta north of the Montana border. Two mines exist in this area, Korite International and the Aurora Ammolite mine.
Ammolite, the gemstone, is not considered a fossil, but whole ammonites with an ammolite exterior are considered a fossil and require a permit to be exported out of Alberta.