Comparison · Organic Gem Materials vs Igneous Rocks
Jet vs Obsidian
Jet and Obsidian are easy to confuse. Obsidian is harder (Mohs 5.5) than Jet (Mohs 3), so Obsidian will scratch Jet and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Jet and Obsidian
- Obsidian is harder (Mohs 5.5) than Jet (Mohs 3), so Obsidian will scratch Jet and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
- Streak color differs: Jet leaves a brown streak on unglazed porcelain, Obsidian leaves white.
- Luster is different: Jet is waxy while Obsidian is vitreous.
- Obsidian feels noticeably heavier for its size (specific gravity 2.4 versus 1.3 for Jet).
- Hold a thin edge to the light: Jet is opaque, Obsidian is translucent.
- They overlap in black and brown, but Obsidian also comes in green and multicolored.
Jet vs Obsidian properties
| Property | Jet | Obsidian |
|---|---|---|
| Type | Organic Gem Materials | Igneous Rocks |
| Mohs hardness | 3 | 5.5 |
| Luster | waxy | vitreous |
| Streak | Brown | White |
| Transparency | opaque | translucent |
| Specific gravity | 1.3 | 2.4 |
| Crystal system | amorphous | amorphous |
| Common colors | Black, Dark brown | Black, Brown, Green, Rainbow |
| Rarity | uncommon | common |
| Typical specimen value | $5–$300+ | $5–$100+ |
Which is more valuable?
Jet is usually the more valuable of the two: a typical collector specimen runs about $40 against $20 for Obsidian, and premium Jet can reach $300 or more.
About Jet
Jet is a compact, lightweight black organic gem material formed from fossilized wood. It takes a high polish, feels warm to the touch, and has been used for mourning jewelry and ornaments since antiquity.
About Obsidian
Obsidian is a naturally occurring volcanic glass formed from rapidly cooled lava. Its sharp edges made it invaluable for ancient tools and weapons.
Jet vs Obsidian FAQ
Is Jet the same as Obsidian?
No. Jet is a organic gem material while Obsidian is a igneous rock. Obsidian is harder (Mohs 5.5) than Jet (Mohs 3), so Obsidian will scratch Jet and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
How can you tell Jet from Obsidian?
Obsidian is harder (Mohs 5.5) than Jet (Mohs 3), so Obsidian will scratch Jet and not the other way round. A copper coin (Mohs 3.5) scratches it, but a fingernail does not. Streak color differs: Jet leaves a brown streak on unglazed porcelain, Obsidian leaves white. Luster is different: Jet is waxy while Obsidian is vitreous.
Which is harder, Jet or Obsidian?
Obsidian is harder: Mohs 5.5 against Mohs 3 for Jet.
Which is more valuable, Jet or Obsidian?
Jet is usually the more valuable of the two: a typical collector specimen runs about $40 against $20 for Obsidian, and premium Jet can reach $300 or more.
