Ammonite
Ammonite is fossil (cephalopod shell), CaCO₃ (aragonite/calcite). In the hand, it rates 3.5 to 4 on the Mohs scale, and it runs brown and tan. Coiled ribbed spiral shell, often cut and polished to show chambered internal whorls. Marine sediments worldwide; notable: Madagascar, Morocco, England, Alberta (Canada).
The geology.
Ammonite carries the formula CaCO₃ (aragonite/calcite). It belongs to the, system. Catalogues list it as fossil (cephalopod shell).
It sits at 3.5 to 4 on the Mohs scale. The surface reads pearly to dull. Light behaviour is opaque. Specific gravity runs 2.6 to 2.8. The streak is white. It breaks with uneven fracture.
Coiled ribbed spiral shell, often cut and polished to show chambered internal whorls.
It reaches buyers as whole polished fossils, split pairs, slices or pendants.
The origins.
Marine sediments worldwide; notable: Madagascar, Morocco, England, Alberta (Canada).
On value, the database notes: common and affordable; gem ammolite is prized.
Traditional associations.
In energy work traditions, associated with cycles and gradual transformation.
We keep this section because people ask. It sits below the geology on purpose, and none of it describes something the stone does.
Spotting the real thing.
Coiled ribbed spiral shell, often cut and polished to show chambered internal whorls.
Cheap 'ammonites' can be resin casts; Moroccan ones sometimes have carved-in or painted detail.
| Looks like | How to tell them apart |
|---|---|
| Resin replica | Casts feel warm and light, with identical 'twins' and no crystalline chamber fill |
| Nautilus shell | Modern nautilus is lightweight recent shell, not stone |
| Snail fossils | Gastropods coil in a rising spiral; ammonites coil flat in one plane |
At-home tests.
Before anyone talks you into a lab report, these are the checks worth doing yourself on ammonite.
| Test | What you should see |
|---|---|
| By touch | Cold and stone-heavy for size |
| Acid check | Chamber fills fizz with vinegar (carbonate) |
| By eye | Suture lines are intricate and irregular, hard to fake |
Stop short of anything that leaves a mark. A gemologist can answer the rest without damaging the stone.
Care & handling.
At 3.5 to 4 on the Mohs scale this is a soft material. Keep it as a display piece, store it apart from harder stones, and skip daily-wear settings.
It breaks with uneven fracture, which is worth knowing before you set it or drop it.
Skip the ultrasonic. Lukewarm water, mild soap and a soft cloth handle routine cleaning without risk.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is CaCO₃ (aragonite/calcite). Crystal system:,. Specific gravity: 2.6 to 2.8. Streak: White. Cleavage and fracture: Uneven fracture.
How it reaches the market
Marine sediments worldwide; notable: Madagascar, Morocco, England, Alberta (Canada).
What it gets confused with
Resin replica: Casts feel warm and light, with identical 'twins' and no crystalline chamber fill. Nautilus shell: Modern nautilus is lightweight recent shell, not stone. Snail fossils: Gastropods coil in a rising spiral; ammonites coil flat in one plane.
What it is worth
Common and affordable; gem ammolite is prized.
Where buyers get caught
Cheap 'ammonites' can be resin casts; Moroccan ones sometimes have carved-in or painted detail.
One more thing
Iridescent ammonite shell from Alberta is the official gemstone 'ammolite', one of the few biologic gems recognized since 1981.
An education-first guide.
We do not carry ammonite. This page exists because the question comes up and the honest answer is worth writing down, whether or not there is anything here to sell you.
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