RocksdayGraptolite vs Shale
To tell Graptolite from Shale: Plain shale has no regular saw-tooth marks.
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
Compacted mud and clay that splits into thin layers. The most common sedimentary rock.
Photo: James St. John, CC BY 2.0
Key differences
- Plain shale has no regular saw-tooth marks.
Side by side
| Property | Graptolite | Shale |
|---|---|---|
| Type | Fossil | Sedimentary rock |
| Mohs hardness | 2–3 | 3 |
| Luster | Dull | Dull |
| Colors | Black, Gray, White | Gray, Black, Red, Green |
| Crystal system / structure | Carbon film on shale | Clastic, very fine, splits in layers |
| Specific gravity | 2.4–2.7 | 2.4–2.8 |
| Found in | Dob's Linn, Scotland; New York | Burgess Shale, British Columbia; Marcellus, Pennsylvania |
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 shale
- Splits into thin, flat flakes along its layers.
- Grains too small to see.
- Smells earthy when wet.
- Soft and crumbly at edges.
Structure: Clastic, very fine, splits in layers
Full Shale guide →More comparisons
Frequently asked questions
What is the difference between graptolite and shale?
Graptolite is a fossil with a Mohs hardness of about 2–3 and a dull luster, usually black, gray or white. Shale is a sedimentary rock with a Mohs hardness of about 3 and a dull luster, usually gray, black, red or green.
How can you tell graptolite from shale?
Plain shale has no regular saw-tooth marks.
Could you tell them apart from a blurry close-up?
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