RocksdayDiopside vs Olivine
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
Olive-green silicate that makes up most of Earth's upper mantle. Gem-quality olivine is called peridot.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Streak (rub on unglazed porcelain): Diopside leaves a white to greenish streak; Olivine leaves white.
Key differences
- Peridot is yellower and lacks cleavage.
Side by side
| Property | Diopside | Olivine |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5.5–6.5 | 6.5–7 |
| Luster | Vitreous | Vitreous |
| Streak | White to greenish | White |
| Colors | Green, Black, White | Green, Yellow |
| Crystal system | Monoclinic | Orthorhombic |
| Specific gravity | 3.22–3.38 | 3.2–4.4 |
| Formula | CaMgSi₂O₆ | (Mg,Fe)₂SiO₄ |
| Found in | Yakutia, Siberia; Pakistan | Papakōlea, Hawaii; San Carlos, Arizona |
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 olivine
- Bottle- to olive-green glassy grains.
- Often as sugary green clumps in black basalt.
- No cleavage — breaks like glass.
- Hard enough to scratch glass.
Crystal system: Orthorhombic
Full Olivine guide →More comparisons
Could you tell them apart from a blurry close-up?
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