Comparison · Igneous Rocks
Rainbow Obsidian vs Peridotite
Rainbow Obsidian and Peridotite are easy to confuse because both are igneous rocks. Both sit near Mohs 5.5, 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 Rainbow Obsidian and Peridotite
- Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Peridotite feels noticeably heavier for its size (specific gravity 3.1–3.4 versus 2.4 for Rainbow Obsidian).
- Hold a thin edge to the light: Rainbow Obsidian is opaque, Peridotite is Opaque.
- They overlap in black, green, and yellow, but Rainbow Obsidian also comes in multicolored and purple.
Rainbow Obsidian vs Peridotite properties
| Property | Rainbow Obsidian | Peridotite |
|---|---|---|
| Type | Igneous Rocks | Igneous Rocks |
| Mohs hardness | 5.5 | 5.5–7 |
| Luster | vitreous | Vitreous (olivine and pyroxene grains) |
| Streak | White | — |
| Transparency | opaque | Opaque |
| Specific gravity | 2.4 | 3.1–3.4 |
| Crystal system | amorphous | — |
| Common colors | Black with rainbow sheen, Purple, Green, Gold | Green, Dark green, Yellowish green, Black |
| Rarity | uncommon | common |
| Typical specimen value | $10–$200+ | $1–$75+ |
Which is more valuable?
Rainbow Obsidian is usually the more valuable of the two: a typical collector specimen runs about $50 against $10 for Peridotite, and premium Rainbow Obsidian can reach $200 or more.
About Rainbow Obsidian
Rainbow obsidian is a type of volcanic glass that displays bands of colorful iridescence when polished and viewed in bright light.
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.
Rainbow Obsidian vs Peridotite FAQ
Is Rainbow Obsidian 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 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Rainbow Obsidian from Peridotite?
Both sit near Mohs 5.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Peridotite feels noticeably heavier for its size (specific gravity 3.1–3.4 versus 2.4 for Rainbow Obsidian). Hold a thin edge to the light: Rainbow Obsidian is opaque, Peridotite is Opaque.
Which is harder, Rainbow Obsidian or Peridotite?
Peridotite is harder: Mohs 5.5–7 against Mohs 5.5 for Rainbow Obsidian.
Which is more valuable, Rainbow Obsidian or Peridotite?
Rainbow Obsidian is usually the more valuable of the two: a typical collector specimen runs about $50 against $10 for Peridotite, and premium Rainbow Obsidian can reach $200 or more.
