Ammolite
Definition and meaning of Ammolite in chemistry.
Ammolite is an opalescent gemstone composed primarily of aragonite, formed from the fossilized shells of ammonites. It displays vibrant iridescent colors and is primarily found in Alberta, Canada.
In more detail
The colorful appearance of ammolite results from thin-film interference within the layered aragonite structure of the fossilized ammonite shell. Over millions of years during the fossilization process, the original shell material has been partially replaced or infused with silica and other minerals while maintaining its remarkable iridescent optical properties. This gemstone is highly prized in jewelry for its unique color displays, which can range from vivid greens and deep reds to brilliant golds and electric blues depending on viewing angle and light source. The Bearpaw Formation in Alberta is the primary source of gem-quality ammolite.
Key facts
| Chemical Composition | Primarily CaCO3 (aragonite) with silica and other minerals |
|---|---|
| Primary Source | Bearpaw Formation, Alberta, Canada |
| Optical Property | Iridescence and opalescence |
| Field | Inorganic Chemistry |
A piece of ammolite from the Canadian Rockies might display a shifting pattern of emerald green and deep red colors when rotated in light, creating the same type of play-of-color seen in fine opals.
Frequently asked questions
How old is ammolite?
Ammolite specimens are typically 70–80 million years old, originating from the Late Cretaceous period.
Why does ammolite display different colors?
The colors result from thin-film interference within the layered aragonite structure; different layer thicknesses and viewing angles produce different colors.