RocksdayCalcite vs Rhodochrosite
How to tell them apart
One of the most common minerals on Earth and the main ingredient of limestone and marble. It breaks into perfect slanted boxes (rhombs) and fizzes in acid.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A manganese carbonate in raspberry-red crystals or rose-and-white banded stalactites.
Photo: JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0
Quick tests
- Acid (vinegar or dilute HCl): Calcite fizzes; Rhodochrosite doesn't.
- Heft: Rhodochrosite feels noticeably heavier for its size (specific gravity 3.5–3.7 vs 2.71).
Key differences
- Pink calcite is paler and lighter in weight.
Side by side
| Property | Calcite | Rhodochrosite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3 | 3.5–4 |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Colors | Clear, White, Orange, Yellow, Blue, Green | Pink, Red |
| Crystal system | Trigonal | Trigonal |
| Specific gravity | 2.71 | 3.5–3.7 |
| Formula | CaCO₃ | MnCO₃ |
| Found in | Iceland; Chihuahua, Mexico | Capillitas, Argentina; Sweet Home Mine, Colorado |
Properties that are the same for both are grayed out.
How to identify calcite
- Fizzes in cold dilute hydrochloric acid (or slowly in vinegar).
- Breaks into rhomb-shaped pieces along three cleavage planes.
- Hardness 3 — a copper coin barely scratches it, a knife easily does.
- Clear pieces show double images of text underneath.
Crystal system: Trigonal
Full Calcite guide →How to identify rhodochrosite
- Rose-pink to red, often banded.
- Rhomb-shaped crystals and cleavage.
- Fizzes in warm acid.
- Soft — a knife scratches it.
Crystal system: Trigonal
Full Rhodochrosite guide →More comparisons
Could you tell them apart from a blurry close-up?
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