RocksdayCalcite vs Witherite
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
Barium carbonate: heavy, pale, and often in six-sided twinned pyramids.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Heft: Witherite feels noticeably heavier for its size (specific gravity 4.3 vs 2.71).
Key differences
- Calcite is much lighter.
Side by side
| Property | Calcite | Witherite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3 | 3–3.5 |
| Luster | Vitreous | Vitreous to resinous |
| Streak | White | White |
| Colors | Clear, White, Orange, Yellow, Blue, Green | White, Gray, Yellow |
| Crystal system | Trigonal | Orthorhombic |
| Specific gravity | 2.71 | 4.3 |
| Formula | CaCO₃ | BaCO₃ |
| Found in | Iceland; Chihuahua, Mexico | Northumberland, England; Cave-in-Rock, Illinois |
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 witherite
- Heavy pale crystals, often double pyramids.
- Fizzes in acid.
- May glow under UV.
Crystal system: Orthorhombic
Full Witherite guide →More comparisons
Could you tell them apart from a blurry close-up?
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