RocksdayCalcite vs Halite
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
Natural table salt. It forms thick beds where ancient seas dried up and grows as cubes, sometimes with stair-stepped 'hopper' faces.
Photo: Lech Darski, CC BY-SA 4.0
Quick tests
- Fingernail: A fingernail scratches Halite (Mohs 2–2.5) but not Calcite (Mohs 3).
- Acid (vinegar or dilute HCl): Calcite fizzes; Halite doesn't.
Key differences
- Halite tastes salty, breaks into cubes and dissolves in water.
- Calcite has no taste, cleaves into slanted rhombs and fizzes in acid.
Side by side
| Property | Calcite | Halite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3 | 2–2.5 |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Colors | Clear, White, Orange, Yellow, Blue, Green | Clear, White, Pink, Orange |
| Crystal system | Trigonal | Cubic |
| Specific gravity | 2.71 | 2.17 |
| Formula | CaCO₃ | NaCl |
| Found in | Iceland; Chihuahua, Mexico | Wieliczka, Poland; Khewra, Pakistan |
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 halite
- Tastes salty.
- Breaks into cubes.
- Dissolves in water.
- Soft — a fingernail almost scratches it.
Crystal system: Cubic
Full Halite guide →More comparisons
Could you tell them apart from a blurry close-up?
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