RocksdayAmber vs Opal
How to tell them apart
Fossilized tree resin, millions of years old. It sometimes traps insects, feathers and plants in perfect detail.
Photo: Anders L. Damgaard - www.amber-inclusions.dk - Baltic-amber-beetle, CC BY-SA 4.0
Hydrated silica with no crystal structure. In precious opal, stacked microscopic spheres split light into flashing rainbow patches.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Fingernail: A fingernail scratches Amber (Mohs 2–2.5) but not Opal (Mohs 5.5–6.5).
- Heft: Opal feels noticeably heavier for its size (specific gravity 1.9–2.3 vs 1.05–1.1).
Key differences
- Fire opal is harder, heavier and sinks in salt water.
Side by side
| Property | Amber | Opal |
|---|---|---|
| Type | Mineraloid | Mineraloid |
| Mohs hardness | 2–2.5 | 5.5–6.5 |
| Luster | Resinous | Vitreous to waxy |
| Streak | White | White |
| Colors | Yellow, Orange, Brown | White, Black, Orange |
| Crystal system / structure | Amorphous (organic) | Amorphous |
| Specific gravity | 1.05–1.1 | 1.9–2.3 |
| Formula | — | SiO₂·nH₂O |
| Found in | Baltic Sea coast; Dominican Republic | Coober Pedy, Australia; Lightning Ridge, Australia |
Properties that are the same for both are grayed out.
How to identify amber
- Warm to the touch and very light.
- Floats in salty water.
- Smells like pine when rubbed hard or heated.
- May contain bubbles or ancient insects.
Structure: Amorphous (organic)
Full Amber guide →How to identify opal
- Flashes of spectral color that shift as you turn it.
- Waxy to glassy luster.
- Light in weight for a gemstone.
- Common opal lacks color play and looks milky.
Structure: Amorphous
Full Opal guide →More comparisons
Could you tell them apart from a blurry close-up?
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