Comparison · Metamorphic Rocks vs Igneous Rocks
Eclogite vs Peridotite
Eclogite and Peridotite are easy to confuse. Both sit near Mohs 6–7.5, 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 Eclogite and Peridotite
- Both sit near Mohs 6–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- They overlap in green, but Eclogite also comes in red and multicolored and Peridotite also comes in yellow and black.
Eclogite vs Peridotite properties
| Property | Eclogite | Peridotite |
|---|---|---|
| Type | Metamorphic Rocks | Igneous Rocks |
| Mohs hardness | 6–7.5 | 5.5–7 |
| Luster | Vitreous (garnet and omphacite grains) | Vitreous (olivine and pyroxene grains) |
| Transparency | Opaque | Opaque |
| Specific gravity | 3.3–3.6 | 3.1–3.4 |
| Common colors | Green (omphacite), Red (garnet), Mottled green and red | Green, Dark green, Yellowish green, Black |
| Rarity | common | common |
| Typical specimen value | $1–$75+ | $1–$75+ |
Which is more valuable?
Typical specimens of Eclogite and Peridotite trade in a similar range, around $10.
About Eclogite
Eclogite is a dense, coarse-grained metamorphic rock composed primarily of red garnet and green sodium-rich pyroxene called omphacite, formed only under the extreme pressures found deep within the crust or upper mantle. Its striking red-and-green coloration makes it one of the most visually distinctive metamorphic rocks, and its mineralogy records some of the highest-pressure conditions preserved in rocks that return to Earth's surface. Eclogite forms from basaltic protoliths subjected to pressures typically exceeding those of ordinary regional metamorphism.
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.
Eclogite vs Peridotite FAQ
Is Eclogite the same as Peridotite?
No. Eclogite is a metamorphic rock while Peridotite is a igneous rock. Both sit near Mohs 6–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Eclogite from Peridotite?
Both sit near Mohs 6–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. They overlap in green, but Eclogite also comes in red and multicolored and Peridotite also comes in yellow and black.
Which is harder, Eclogite or Peridotite?
Eclogite is harder: Mohs 6–7.5 against Mohs 5.5–7 for Peridotite.
Which is more valuable, Eclogite or Peridotite?
Typical specimens of Eclogite and Peridotite trade in a similar range, around $10.
