Crystal & mineral guide
Ammonite
Ammonoidea (extinct cephalopod)
Extinct coiled cephalopod fossil — ammolite is the iridescent gem variety.
Identify Ammonite with RockScanAbout Ammonite
Ammonites are extinct shelled cephalopods with coiled chambers. Moroccan and Madagascan cut halves are trade staples. Canadian ammolite is a gem-quality iridescent ammonite shell. Suture patterns help species ID for paleontology buyers.
Ammonite belongs in a crystal identifier workflow because photo cues — color zoning, crystal habit, and surface luster — combine with measurable traits like Mohs 3–4 (mineralized) and specific gravity 2.4–2.8. Use RockScan’s camera to get a first-pass ID, then confirm with the checklist below.
Ammonite properties
| Mohs hardness | 3–4 (mineralized) |
|---|---|
| Crystal system | Fossil aggregate |
| Luster | Dull to nacreous (ammatite/ammolite) |
| Color | Brown, gray; iridescent ammolite |
| Composition | Calcite/aragonite replaced shell; sometimes pyrite |
| Formation | Marine sedimentary burial of cephalopod shells |
| Occurrence | Morocco, Madagascar, Canada (ammolite), UK |
| Specific gravity | 2.4–2.8 |
| Cleavage | None |
How to identify Ammonite
- Coiled chambered shell
- Suture lines on internal molds
- Iridescence indicates ammolite-grade nacre
Collector notes
- Went extinct at the end-Cretaceous with non-avian dinosaurs
- Ammolite is a legally recognized gemstone material
Value context: Complete aesthetic pairs and gem ammolite command the highest prices.
Ammonite FAQ
How do you identify Ammonite?
Ammonite (Ammonoidea (extinct cephalopod)) is typically recognized by brown, gray; iridescent ammolite color, dull to nacreous (ammatite/ammolite) luster, Mohs hardness 3–4 (mineralized), and fossil aggregate crystal system. RockScan can suggest Ammonite from a photo and surface these checks on the result card.
What is Ammonite made of?
Ammonite composition: Calcite/aragonite replaced shell; sometimes pyrite. It forms via marine sedimentary burial of cephalopod shells and is found in Morocco, Madagascar, Canada (ammolite), UK.
Is Ammonite valuable?
Complete aesthetic pairs and gem ammolite command the highest prices.
