RocksdayBaculites vs Goniatite
The quickest way to tell Baculites from Goniatite: Goniatite fizzes; Baculites doesn't.
A straight-shelled ammonite from the Cretaceous. The shell is a long cone with complex, wavy suture lines.
Photo: DanielCD, CC BY-SA 3.0
An early ammonoid with a coiled shell and simple zigzag sutures, common in Paleozoic rocks.
Photo: James St. John, CC BY 2.0
Quick tests
- Acid (vinegar or dilute HCl): Goniatite fizzes; Baculites doesn't.
Key differences
- Baculites is straight, not coiled.
Side by side
| Property | Baculites | Goniatite |
|---|---|---|
| Type | Fossil | Fossil |
| Mohs hardness | 3–4 | 3–4 |
| Luster | Dull to pearly | Dull |
| Colors | Gray, Brown, White, Gold | Gray, Brown, White |
| Crystal system / structure | Straight ammonite shell | Coiled shell with zigzag sutures |
| Specific gravity | 2.6–2.8 | 2.6–2.8 |
| Found in | Pierre Shale, South Dakota; Montana | Morocco; Oklahoma |
Properties that are the same for both are grayed out.
How to identify baculites
- A straight section of shell, not a coil.
- Wavy, branching suture lines where the chambers met the shell.
- Often in shale. Shell material may fizz; a mold may not.
Structure: Straight ammonite shell
Full Baculites guide →How to identify goniatite
- A coil, often preserved as a disk.
- Sutures are sharp zigzags, not the leafy frills of later ammonites.
- Shell material fizzes in acid.
Structure: Coiled shell with zigzag sutures
Full Goniatite guide →More comparisons
Frequently asked questions
What is the difference between baculites and goniatite?
Baculites is a fossil with a Mohs hardness of about 3–4 and a dull to pearly luster, usually gray, brown, white or golden. Goniatite is a fossil with a Mohs hardness of about 3–4 and a dull luster, usually gray, brown or white.
How can you tell baculites from goniatite?
Goniatite fizzes; Baculites doesn't. Baculites is straight, not coiled.
Could you tell them apart from a blurry close-up?
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