Comparison · Sedimentary Rocks
Limestone vs Marl
Limestone and Marl are easy to confuse because both are sedimentary rocks. Both sit near Mohs 3, 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 Limestone and Marl
- Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Streak color differs: Limestone leaves a white streak on unglazed porcelain, Marl leaves white to light gray.
- They overlap in white, gray, and brown, but Limestone also comes in yellow and Marl also comes in green.
Limestone vs Marl properties
| Property | Limestone | Marl |
|---|---|---|
| Type | Sedimentary Rocks | Sedimentary Rocks |
| Mohs hardness | 3 | 2.5 |
| Luster | dull | dull |
| Streak | White | White to light gray |
| Transparency | opaque | opaque |
| Specific gravity | 2.7 | 2.4 |
| Crystal system | varies | varies |
| Common colors | White, Gray, Tan, Yellow | Gray, Cream, White, Tan, Greenish gray |
| Rarity | common | common |
| Typical specimen value | $1–$50+ | $1–$75+ |
Which is more valuable?
Typical specimens of Limestone and Marl trade in a similar range, around $10.
About Limestone
Limestone is a sedimentary rock composed mainly of calcium carbonate. It often contains fossils and is the precursor to marble.
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.
Limestone vs Marl FAQ
Is Limestone the same as Marl?
No. Both are sedimentary rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Limestone from Marl?
Both sit near Mohs 3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Streak color differs: Limestone leaves a white streak on unglazed porcelain, Marl leaves white to light gray. They overlap in white, gray, and brown, but Limestone also comes in yellow and Marl also comes in green.
Which is harder, Limestone or Marl?
Limestone is harder: Mohs 3 against Mohs 2.5 for Marl.
Which is more valuable, Limestone or Marl?
Typical specimens of Limestone and Marl trade in a similar range, around $10.
