RocksdayChert vs Jasper
How to tell them apart
A hard sedimentary rock of microscopic quartz. Dark nodules in chalk are called flint.
Photo: Unknown, Public domain
Opaque, impurity-rich microcrystalline quartz. Iron oxides give the classic brick red, but jasper comes in nearly every earthy color and pattern.
Photo: Tommy from Arad, CC BY 2.0
Quick tests
- Texture: Chert is a rock — a mix of grains or minerals; Jasper is a single mineral.
Key differences
- Jasper is a colorful variety — chert is usually gray or black.
Side by side
| Property | Chert | Jasper |
|---|---|---|
| Type | Sedimentary rock | Mineral |
| Mohs hardness | 6.5–7 | 6.5–7 |
| Luster | Waxy to dull | Dull to waxy |
| Streak | — | White |
| Colors | Gray, Black, Brown, White | Red, Brown, Yellow, Green |
| Crystal system / structure | Microcrystalline quartz | Microcrystalline quartz (chalcedony) |
| Specific gravity | 2.5–2.7 | 2.5–2.9 |
| Formula | — | SiO₂ + impurities |
| Found in | Flint Ridge, Ohio; Alibates, Texas | Oregon and Idaho; India |
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 jasper
- Completely opaque, even at thin edges.
- Solid earthy colors, often red, sometimes patterned.
- Hard — scratches glass.
- Smooth, curved fracture surfaces.
Crystal system: Microcrystalline quartz (chalcedony)
Full Jasper guide →More comparisons
Could you tell them apart from a blurry close-up?
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