Comparison · Sedimentary Rocks
Dolostone vs Marl
Dolostone and Marl are easy to confuse because both are sedimentary rocks. Dolostone is harder (Mohs 3.5) than Marl (Mohs 2.5), so Dolostone will scratch Marl and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Dolostone and Marl
- Dolostone is harder (Mohs 3.5) than Marl (Mohs 2.5), so Dolostone will scratch Marl and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
- Streak color differs: Dolostone leaves a white streak on unglazed porcelain, Marl leaves white to light gray.
- They overlap in brown, gray, and white, but Marl also comes in green.
Dolostone vs Marl properties
| Property | Dolostone | Marl |
|---|---|---|
| Type | Sedimentary Rocks | Sedimentary Rocks |
| Mohs hardness | 3.5 | 2.5 |
| Luster | dull | dull |
| Streak | White | White to light gray |
| Transparency | opaque | opaque |
| Specific gravity | 2.85 | 2.4 |
| Crystal system | varies | varies |
| Common colors | Tan, Gray, White, Cream, Brown | Gray, Cream, White, Tan, Greenish gray |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Dolostone and Marl trade in a similar range, around $10.
About Dolostone
Dolostone is a carbonate sedimentary rock composed mostly of the mineral dolomite. It often resembles limestone but may react more weakly with dilute acid.
About Marl
Marl is an earthy sedimentary rock or sediment made of mixed clay and calcium carbonate. It often looks gray, cream, tan, or soft and chalky.
Dolostone vs Marl FAQ
Is Dolostone the same as Marl?
No. Both are sedimentary rocks, but they are distinct rock types with different hardness, streak or luster. Dolostone is harder (Mohs 3.5) than Marl (Mohs 2.5), so Dolostone will scratch Marl and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
How can you tell Dolostone from Marl?
Dolostone is harder (Mohs 3.5) than Marl (Mohs 2.5), so Dolostone will scratch Marl and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Streak color differs: Dolostone leaves a white streak on unglazed porcelain, Marl leaves white to light gray. They overlap in brown, gray, and white, but Marl also comes in green.
Which is harder, Dolostone or Marl?
Dolostone is harder: Mohs 3.5 against Mohs 2.5 for Marl.
Which is more valuable, Dolostone or Marl?
Typical specimens of Dolostone and Marl trade in a similar range, around $10.
