RocksdayChert vs Novaculite
How to tell them apart
A hard sedimentary rock of microscopic quartz. Dark nodules in chalk are called flint.
Photo: Unknown, Public domain
An extremely fine, dense quartz rock famous as a whetstone.
Photo: James St. John, CC BY 2.0
Key differences
- Chert is similar; novaculite is whiter and more uniform.
Side by side
| Property | Chert | Novaculite |
|---|---|---|
| Type | Sedimentary rock | Sedimentary rock |
| Mohs hardness | 6.5–7 | 7 |
| Luster | Waxy to dull | Waxy |
| Colors | Gray, Black, Brown, White | White, Gray, Black |
| Crystal system / structure | Microcrystalline quartz | Dense microcrystalline quartz |
| Specific gravity | 2.5–2.7 | 2.6–2.65 |
| Found in | Flint Ridge, Ohio; Alibates, Texas | Ouachita Mountains, Arkansas; Texas |
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 novaculite
- White to gray, smooth and waxy.
- Very hard; breaks with sharp edges.
- No visible grains.
Structure: Dense microcrystalline quartz
Full Novaculite guide →More comparisons
Could you tell them apart from a blurry close-up?
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