RocksdayDunite vs Olivine
How to tell them apart
A rock that is more than 90% olivine, bright green inside and tan on the outside.
Photo: B.navez, 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
- Texture: Dunite is a rock — a mix of grains or minerals; Olivine is a single mineral.
Key differences
- Olivine is the single mineral; dunite is the rock made of it.
Side by side
| Property | Dunite | Olivine |
|---|---|---|
| Type | Igneous rock | Mineral |
| Mohs hardness | 6.5–7 | 6.5–7 |
| Luster | Vitreous to granular | Vitreous |
| Streak | — | White |
| Colors | Green, Yellow, Brown | Green, Yellow |
| Crystal system / structure | Coarse-grained (ultramafic) | Orthorhombic |
| Specific gravity | 3.2–3.4 | 3.2–4.4 |
| Formula | — | (Mg,Fe)₂SiO₄ |
| Found in | Dun Mountain, New Zealand; Twin Sisters, Washington | Papakōlea, Hawaii; San Carlos, Arizona |
Properties that are the same for both are grayed out.
How to identify dunite
- Sugary green olivine throughout.
- Tan, sandpapery weathered rind.
- Very heavy.
Structure: Coarse-grained (ultramafic)
Full Dunite 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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