Comparison · Sedimentary Rocks
Diatomite vs Oolite
Diatomite and Oolite are easy to confuse because both are sedimentary rocks. Oolite is harder (Mohs 3) than Diatomite (Mohs 1.5), so Oolite will scratch Diatomite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Diatomite and Oolite
- Oolite is harder (Mohs 3) than Diatomite (Mohs 1.5), so Oolite will scratch Diatomite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
- Streak color differs: Diatomite leaves a white streak on unglazed porcelain, Oolite leaves white to light-colored.
- Oolite feels noticeably heavier for its size (specific gravity 2.7 versus 1 for Diatomite).
Diatomite vs Oolite properties
| Property | Diatomite | Oolite |
|---|---|---|
| Type | Sedimentary Rocks | Sedimentary Rocks |
| Mohs hardness | 1.5 | 3 |
| Luster | dull | dull |
| Streak | White | White to light-colored |
| Transparency | opaque | opaque |
| Specific gravity | 1 | 2.7 |
| Crystal system | varies | varies |
| Common colors | White, Cream, Light gray, Tan | White, Cream, Tan, Gray, Brown |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Diatomite and Oolite trade in a similar range, around $10.
About Diatomite
Diatomite is a very light, porous, chalky sedimentary rock made mostly of microscopic diatom remains.
About Oolite
Oolite is a sedimentary rock made of tiny rounded coated grains called ooids, often forming oolitic limestone.
Diatomite vs Oolite FAQ
Is Diatomite the same as Oolite?
No. Both are sedimentary rocks, but they are distinct rock types with different hardness, streak or luster. Oolite is harder (Mohs 3) than Diatomite (Mohs 1.5), so Oolite will scratch Diatomite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
How can you tell Diatomite from Oolite?
Oolite is harder (Mohs 3) than Diatomite (Mohs 1.5), so Oolite will scratch Diatomite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Streak color differs: Diatomite leaves a white streak on unglazed porcelain, Oolite leaves white to light-colored. Oolite feels noticeably heavier for its size (specific gravity 2.7 versus 1 for Diatomite).
Which is harder, Diatomite or Oolite?
Oolite is harder: Mohs 3 against Mohs 1.5 for Diatomite.
Which is more valuable, Diatomite or Oolite?
Typical specimens of Diatomite and Oolite trade in a similar range, around $10.
