RocksdayAzurite vs Chalcanthite
How to tell them apart
An intensely deep blue copper carbonate. Over time it slowly converts to green malachite, and the two are often found together.
Photo: Ivar Leidus, CC BY-SA 4.0
Water-soluble copper sulfate. Natural crusts form on mine walls; big blue crystals in shops are lab-grown.
Photo: Didier Descouens, CC BY-SA 3.0
Quick tests
- Fingernail: A fingernail scratches Chalcanthite (Mohs 2.5) but not Azurite (Mohs 3.5–4).
- Acid (vinegar or dilute HCl): Azurite fizzes; Chalcanthite doesn't.
- Streak (rub on unglazed porcelain): Azurite leaves a light blue streak; Chalcanthite leaves white.
- Heft: Azurite feels noticeably heavier for its size (specific gravity 3.77–3.78 vs 2.12–2.3).
Key differences
- Azurite is darker blue, doesn't dissolve and fizzes in acid.
Side by side
| Property | Azurite | Chalcanthite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3.5–4 | 2.5 |
| Luster | Vitreous | Vitreous |
| Streak | Light blue | White |
| Colors | Blue | Blue |
| Crystal system | Monoclinic | Triclinic |
| Specific gravity | 3.77–3.78 | 2.12–2.3 |
| Formula | Cu₃(CO₃)₂(OH)₂ | CuSO₄·5H₂O |
| Found in | Bisbee, Arizona; Tsumeb, Namibia | Chuquicamata, Chile; Arizona |
Properties that are the same for both are grayed out.
How to identify azurite
- Deep 'azure' blue, often with green malachite.
- Fizzes in acid.
- Soft — a knife scratches it.
- Light blue streak.
Crystal system: Monoclinic
Full Azurite guide →How to identify chalcanthite
- Vivid sky to royal blue.
- Dissolves in water.
- Turns white and powdery when it dries out.
Crystal system: Triclinic
Full Chalcanthite guide →More comparisons
Could you tell them apart from a blurry close-up?
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