Comparison · Igneous Rocks
Dunite vs Peridotite
Dunite and Peridotite are easy to confuse because both are igneous rocks. Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Dunite and Peridotite
- Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Dunite is Opaque (translucent in thin section), Peridotite is Opaque.
- They overlap in green and yellow, but Dunite also comes in brown and Peridotite also comes in black.
Dunite vs Peridotite properties
| Property | Dunite | Peridotite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 6.5–7 | 5.5–7 |
| Luster | Vitreous (olivine grains) | Vitreous (olivine and pyroxene grains) |
| Transparency | Opaque (translucent in thin section) | Opaque |
| Specific gravity | 3.2–3.3 | 3.1–3.4 |
| Common colors | Olive green, Yellowish green, Dark green, Brown (weathered) | Green, Dark green, Yellowish green, Black |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Dunite and Peridotite trade in a similar range, around $10.
About Dunite
Dunite is a coarse-grained ultramafic igneous rock composed almost entirely of olivine, typically more than 90 percent, with minor chromite, pyroxene, or spinel. It represents mantle material or cumulate layers formed by the settling of olivine crystals in a magma chamber, making it one of the most direct samples of Earth's upper mantle available at the surface. Its name comes from Dun Mountain in New Zealand, where it was first described.
About Peridotite
Peridotite is a coarse-grained ultramafic igneous rock composed predominantly of olivine along with varying amounts of pyroxene, making it the principal rock type of Earth's upper mantle. It is dense, dark green to black, and nearly devoid of quartz or feldspar, reflecting a chemical composition far more magnesium- and iron-rich than crustal rocks. Peridotite reaches the surface only through specific tectonic processes, since it normally resides tens of kilometers below the crust.
Dunite vs Peridotite FAQ
Is Dunite the same as Peridotite?
No. Both are igneous rocks, but they are distinct rock types with different hardness, streak or luster. Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Dunite from Peridotite?
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Dunite is Opaque (translucent in thin section), Peridotite is Opaque. They overlap in green and yellow, but Dunite also comes in brown and Peridotite also comes in black.
Which is harder, Dunite or Peridotite?
Dunite is harder: Mohs 6.5–7 against Mohs 5.5–7 for Peridotite.
Which is more valuable, Dunite or Peridotite?
Typical specimens of Dunite and Peridotite trade in a similar range, around $10.
