RocksdayGraptolite vs Knightia
To tell Graptolite from Knightia: Graptolites are saw-blade films, not fish.
Saw-blade or twig-like carbon films on black shale, left by tiny colonial animals. They are classic index fossils.
Photo: Grezmagro, CC BY-SA 4.0
A small extinct herring. The slabs from Wyoming's Green River Formation are the fossil fish people see most often.
Photo: James St. John, CC BY 2.0
Key differences
- Graptolites are saw-blade films, not fish.
Side by side
| Property | Graptolite | Knightia |
|---|---|---|
| Type | Fossil | Fossil |
| Mohs hardness | 2–3 | 2–3 |
| Luster | Dull | Dull |
| Colors | Black, Gray, White | Brown, Gray, Yellow |
| Crystal system / structure | Carbon film on shale | Fish skeleton in shale |
| Specific gravity | 2.4–2.7 | 2.2–2.6 |
| Found in | Dob's Linn, Scotland; New York | Green River Formation, Wyoming |
Properties that are the same for both are grayed out.
How to identify graptolite
- Dark marks like a hacksaw blade, a tuning fork or a twig on shale.
- The fossil is a film, not a raised shell.
- The host rock splits into thin slabs.
Structure: Carbon film on shale
Full Graptolite guide →How to identify knightia
- A complete little fish, often 5–15 cm, in tan or brown shale.
- Scales, ribs and a forked tail still in place.
- The rock is a soft lake shale, not a limestone shell bed.
Structure: Fish skeleton in shale
Full Knightia guide →More comparisons
Frequently asked questions
What is the difference between graptolite and knightia?
Graptolite is a fossil with a Mohs hardness of about 2–3 and a dull luster, usually black, gray or white. Knightia is a fossil with a Mohs hardness of about 2–3 and a dull luster, usually brown, gray or yellow.
How can you tell graptolite from knightia?
Graptolites are saw-blade films, not fish.
Could you tell them apart from a blurry close-up?
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