Ammolite
Ammolite is a rare organic gemstone formed from the fossilized shells of ancient marine animals called ammonites. It is highly valued for its brilliant iridescent colors, which include red, green, blue, and sometimes purple.
About
Ammolite
Ammolite is composed primarily of aragonite, a form of calcium carbonate (CaCO₃), and belongs to the carbonate mineral group. It formed over 70 million years ago during the Late Cretaceous period when ammonite shells were buried under sediment and gradually mineralized. Its crystal system is orthorhombic. The most striking feature of Ammolite is its play of color, caused by light interference within its layered structure. The color range can include bright reds, greens, blues, and yellows, with some rare specimens showing multiple colors at once. This effect is similar to opal but has a more structured pattern. Ammolite has a hardness of about 3.5 to 4 on the Mohs scale, making it relatively soft and fragile compared to other gemstones. Its specific gravity ranges from 2.6 to 2.9, and its refractive index is approximately 1.52 to 1.68.
Physical & Chemical Properties
| Name | Ammolite |
|---|---|
| Scientific Name | Aragonite |
| Mineral Group | Carbonate |
| Hardness (Mohs) | 3.5 – 4 |
| Color | Iridescent (red, green, blue, yellow, purple) |
| Origin | Canada (Alberta – primary source), USA |
| Chemical Formula | CaCO₃ |
Quick Facts
| Crystal System | Orthorhombic |
|---|---|
| Specific Gravity | 2.6 – 2.9 |
| Birthstone | Not a traditional |
| Refractive Index | 1.52 – 1.68 |
| Optical Character | Doubly refractive (anisotropic) |
| Dispersion | Low |
| Major Sources | Canada (Alberta – primary source), USA |
| Treatments | Ammolite is often stabilized with resin or backing materials to improve durability |
| Price Range | $5 to $60 |
| Care Instructions | Avoid heat, chemicals, and prolonged sunlight Clean gently with a soft cloth (no ultrasonic cleaners) Store separately to prevent scratches |