Properties
| Category | fossilized, mineralized Ammonite shell |
|---|---|
| Formula | CaCO; 3 aragonite polymorph, with minor amounts of calcite, pyrite, silica, and other impurities |
| Color | Gray to brown, can be radiant blue, with primarily red to green iridescence. |
| Cleavage | no true cleavage |
| Fracture | uneven to granular |
| Mohs scale hardness | 3.5 - 4.5 |
| Luster | greasy to dull |
| Specific gravity | usually about 2.70 (varies with mineral content) |
From the Wikipedia article
Ammolite is an organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is commonly unearthed by natural erosion or through the process of various mining practices, within the perimeter of an ancient sea bed called the Western Interior Seaway. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell. It is one of few biogenic gemstones; others include amber and pearl.
Source
Source record: crystal-compendium/ammolite/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Ammolite — revision id 1367858668. Text and properties from Wikipedia, licensed CC BY-SA 4.0.