RocksdayKaolinite vs Talc
How to tell them apart
A white clay mineral formed when feldspar weathers. It's the main ingredient of porcelain.
Photo: James St. John https://www.flickr.com/people/jsjgeology?rb=1, CC BY 2.0
The softest mineral, number 1 on the Mohs scale. It feels soapy or greasy and leaves powder on your fingers.
Photo: Unknown, Public domain
Key differences
- Talc feels slippery and isn't plastic when wet.
Side by side
| Property | Kaolinite | Talc |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 2–2.5 | 1 |
| Luster | Earthy | Pearly to greasy |
| Streak | White | White |
| Colors | White, Yellow, Pink | White, Green, Gray |
| Crystal system | Triclinic | Monoclinic |
| Specific gravity | 2.6 | 2.7–2.8 |
| Formula | Al₂Si₂O₅(OH)₄ | Mg₃Si₄O₁₀(OH)₂ |
| Found in | Jingdezhen, China; Cornwall, England | Vermont; Montana |
Properties that are the same for both are grayed out.
How to identify kaolinite
- White, chalky and powdery.
- Smells earthy when breathed on and gets plastic when wet.
- Doesn't fizz in acid.
Crystal system: Triclinic
Full Kaolinite guide →How to identify talc
- Easily scratched by a fingernail.
- Slippery, soapy feel.
- Pearly sheen on flaky surfaces.
- Flakes don't spring back when bent.
Crystal system: Monoclinic
Full Talc guide →More comparisons
Could you tell them apart from a blurry close-up?
Play today's Rocksday