RocksdayDiopside vs Emerald
How to tell them apart
A calcium magnesium pyroxene. Chrome diopside is a vivid green gem; black star diopside comes from India.
Photo: Didier Descouens, CC BY-SA 3.0
Green beryl colored by chromium or vanadium — one of the four classic precious gems.
Photo: Géry PARENT, CC0
Quick tests
- Hardness: Emerald is clearly harder: Mohs 7.5–8 versus 5.5–6.5.
- Streak (rub on unglazed porcelain): Diopside leaves a white to greenish streak; Emerald leaves white.
Key differences
- Emerald is harder and hexagonal.
Side by side
| Property | Diopside | Emerald |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5.5–6.5 | 7.5–8 |
| Luster | Vitreous | Vitreous |
| Streak | White to greenish | White |
| Colors | Green, Black, White | Green |
| Crystal system | Monoclinic | Hexagonal |
| Specific gravity | 3.22–3.38 | 2.67–2.78 |
| Formula | CaMgSi₂O₆ | Be₃Al₂Si₆O₁₈ (with Cr/V) |
| Found in | Yakutia, Siberia; Pakistan | Muzo and Chivor, Colombia; Kafubu, Zambia |
Properties that are the same for both are grayed out.
How to identify diopside
- Bright to bottle green, stubby prisms.
- Two cleavages at nearly 90°.
- Hardness about 6.
Crystal system: Monoclinic
Full Diopside 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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