RocksdayDolostone vs Limestone
How to tell them apart
A limestone-like rock made of the mineral dolomite rather than calcite.
Photo: James St. John, CC BY 2.0
A rock made mostly of calcite, often from shells and skeletons of sea creatures. It dissolves to create caves.
Photo: Mike Davis, CC0
Quick tests
- Acid (vinegar or dilute HCl): Dolostone fizzes weakly, or only when powdered or warmed; Limestone doesn't.
Key differences
- Limestone fizzes vigorously.
Side by side
| Property | Dolostone | Limestone |
|---|---|---|
| Type | Sedimentary rock | Sedimentary rock |
| Mohs hardness | 3.5–4 | 3–4 |
| Luster | Dull to sugary | Dull |
| Colors | Gray, White, Brown | White, Gray, Brown |
| Crystal system / structure | Crystalline carbonate | Varied, often fossiliferous |
| Specific gravity | 2.8–2.9 | 2.5–2.7 |
| Found in | The Dolomites, Italy; Niagara Escarpment | Bedford, Indiana; Tura, Egypt |
Properties that are the same for both are grayed out.
How to identify dolostone
- Gray to cream, often sugary.
- Fizzes only weakly — or only when powdered.
- Weathers to a buff color.
Structure: Crystalline carbonate
Full Dolostone guide →How to identify limestone
- Fizzes in dilute acid.
- Gray to cream, often with shell fossils.
- A knife scratches it.
- Weathers into smooth, pitted surfaces.
Structure: Varied, often fossiliferous
Full Limestone guide →More comparisons
Could you tell them apart from a blurry close-up?
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