RocksdayDioptase vs Emerald
How to tell them apart
An intensely emerald-green copper silicate that forms glittering short crystals.
Photo: Géry PARENT, CC BY-SA 4.0
Green beryl colored by chromium or vanadium — one of the four classic precious gems.
Photo: Géry PARENT, CC0
Quick tests
- Scratch glass: Emerald scratches glass (Mohs 7.5–8); Dioptase can't (Mohs 5).
- Streak (rub on unglazed porcelain): Dioptase leaves a green streak; Emerald leaves white.
Key differences
- Emerald is harder and forms longer prisms.
- Dioptase is softer and forms short rhombic crystals.
Side by side
| Property | Dioptase | Emerald |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5 | 7.5–8 |
| Luster | Vitreous | Vitreous |
| Streak | Green | White |
| Colors | Green | Green |
| Crystal system | Trigonal | Hexagonal |
| Specific gravity | 3.28–3.35 | 2.67–2.78 |
| Formula | CuSiO₂(OH)₂ | Be₃Al₂Si₆O₁₈ (with Cr/V) |
| Found in | Tsumeb, Namibia; Altyn-Tyube, Kazakhstan | Muzo and Chivor, Colombia; Kafubu, Zambia |
Properties that are the same for both are grayed out.
How to identify dioptase
- Vivid emerald green, often a sparkling crystal crust.
- Short six-sided crystals with rhombic tips.
- Hardness 5 — a knife scratches it.
Crystal system: Trigonal
Full Dioptase guide →How to identify emerald
- Deep green six-sided prisms with flat ends.
- Almost always has internal fractures and inclusions.
- Hardness 7.5–8.
Crystal system: Hexagonal
Full Emerald guide →More comparisons
Could you tell them apart from a blurry close-up?
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