RocksdayChert vs Fossil Shark Tooth
How to tell them apart
A hard sedimentary rock of microscopic quartz. Dark nodules in chalk are called flint.
Photo: Unknown, Public domain
Fossilized shark teeth stained black, gray or brown by minerals as they lay buried.
Photo: Wilson44691, CC BY-SA 3.0
Quick tests
- Scratch glass: Chert scratches glass (Mohs 6.5–7); Fossil Shark Tooth can't (Mohs 5).
Key differences
- Chert flakes have no enamel or root.
Side by side
| Property | Chert | Fossil Shark Tooth |
|---|---|---|
| Type | Sedimentary rock | Fossil |
| Mohs hardness | 6.5–7 | 5 |
| Luster | Waxy to dull | Vitreous (enamel) |
| Colors | Gray, Black, Brown, White | Black, Gray, Brown |
| Crystal system / structure | Microcrystalline quartz | Fluorapatite (fossilized tooth) |
| Specific gravity | 2.5–2.7 | 2.9–3.1 |
| Found in | Flint Ridge, Ohio; Alibates, Texas | Venice, Florida; Calvert Cliffs, Maryland |
Properties that are the same for both are grayed out.
How to identify chert
- Breaks with smooth, curved fractures and sharp edges.
- Waxy luster on fresh breaks.
- Scratches glass.
- Sparks when struck against steel.
Structure: Microcrystalline quartz
Full Chert guide →How to identify fossil shark tooth
- Triangular tooth with shiny enamel and a root.
- Usually dark from mineral staining.
- Often serrated edges.
Structure: Fluorapatite (fossilized tooth)
Full Fossil Shark Tooth guide →More comparisons
Could you tell them apart from a blurry close-up?
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