Comparison · Sedimentary Rocks vs Silicate Minerals
Diatomite vs Kaolinite
Diatomite and Kaolinite are easy to confuse. Both sit near Mohs 1.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Diatomite and Kaolinite
- Both sit near Mohs 1.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Kaolinite feels noticeably heavier for its size (specific gravity 2.6 versus 1 for Diatomite).
- They overlap in white and gray, but Diatomite also comes in brown and Kaolinite also comes in yellow.
Diatomite vs Kaolinite properties
| Property | Diatomite | Kaolinite |
|---|---|---|
| Type | Sedimentary Rocks | Silicate Minerals |
| Mohs hardness | 1.5 | 2 |
| Luster | dull | earthy |
| Streak | White | White |
| Transparency | opaque | opaque |
| Specific gravity | 1 | 2.6 |
| Crystal system | varies | triclinic |
| Common colors | White, Cream, Light gray, Tan | White, Cream, Pale yellow, Light gray |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $2–$80+ |
Which is more valuable?
Kaolinite is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Diatomite, and premium Kaolinite can reach $80 or more.
About Diatomite
Diatomite is a very light, porous, chalky sedimentary rock made mostly of microscopic diatom remains.
About Kaolinite
Kaolinite is a soft white clay mineral and the main component of the rock kaolin, or china clay. It forms fine-grained earthy masses produced by the weathering of feldspar-rich rocks and is a key industrial raw material.
Diatomite vs Kaolinite FAQ
Is Diatomite the same as Kaolinite?
No. Diatomite is a sedimentary rock while Kaolinite is a silicate mineral. Both sit near Mohs 1.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Diatomite from Kaolinite?
Both sit near Mohs 1.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Kaolinite feels noticeably heavier for its size (specific gravity 2.6 versus 1 for Diatomite). They overlap in white and gray, but Diatomite also comes in brown and Kaolinite also comes in yellow.
Which is harder, Diatomite or Kaolinite?
Kaolinite is harder: Mohs 2 against Mohs 1.5 for Diatomite.
Which is more valuable, Diatomite or Kaolinite?
Kaolinite is usually the more valuable of the two: a typical collector specimen runs about $15 against $10 for Diatomite, and premium Kaolinite can reach $80 or more.
