Specimen at a glance
| Mineral | Opal (precious) |
|---|---|
| Chemistry | SiO2·nH2O |
| Mohs hardness | 5.5–6.5 |
| Crystal system | Amorphous |
| Locality | Ethiopia |
| Form | Polished / tumbled |
| You receive | The exact specimen pictured |
About this specimen
Fire opal is a variety of opal — hydrated silica (SiO₂·nH₂O) — prized for its warm orange, red, or yellow base color. “Play-of-color” describes the extra flashes of color, often green or blue, that shift as the stone moves; it’s caused by light diffracting off microscopic silica spheres stacked inside the stone. Most fire opal on the market today, including this piece, comes from Ethiopia’s Wollo Province, a source that has produced some of the most vivid fire opal since deposits were discovered there in the late 2000s.
This cabochon has been cut and polished to show its color to best effect, with visible play-of-color across the dome. Ethiopian opal is often “hydrophane,” meaning it’s more porous than opal from some other localities and can absorb water and temporarily cloud or even crack if soaked or exposed to rapid temperature swings — so it’s best kept dry, stored away from direct heat, and cleaned with only a soft, dry cloth rather than water or an ultrasonic cleaner. At Mohs 5.5–6.5, it’s softer than quartz and should be protected from scratches if set into jewelry.
A bright, natural accent stone for a collection, a display cabinet, or a custom jewelry setting.
Inside Fire Opal
The only mineraloid in the shop — opal isn’t even crystalline.
The story: Unlike almost everything else in this shop, opal has no crystal lattice at all — it’s built from microscopic silica spheres stacked together with water trapped in between. When those spheres are perfectly uniform in size, light diffracts through the gaps into the rainbow ‘play-of-color’ seen in precious opal. Fire opal gets its orange-red body color from iron oxide, independent of that diffraction effect.
Why collectors chase it: Play-of-color (when present) is unlike any other optical effect in mineralogy, and fire opal’s saturated orange base color is striking even without it.
Care: The trapped water makes opal genuinely delicate: avoid prolonged dry heat or big temperature swings, which can craze or crack it, and skip ultrasonic cleaners.
Opal: the science
- The flashes of color are diffraction, not pigment. Sphere size decides which colors appear: larger spheres can flash red.
- Much Ethiopian opal is hydrophane, meaning it can absorb water and temporarily change in clarity or play-of-color until it dries out again.
- Opal contains water, commonly several percent by weight, which is why it is sensitive to heat and rapid drying.
Go deeper
Want the full story on opal: how it forms, how to identify it, and what makes a great specimen?
Questions about this piece
What is opal?
Opal is hydrated silica with no crystal structure. Play-of-color happens when light diffracts through orderly stacks of microscopic silica spheres.
Where was it found?
This piece comes from Ethiopia. We list a locality whenever it is known, because where a mineral formed is part of its story and its value.
How hard is it, and how should I care for it?
It rates 5.5–6.5 on the Mohs scale. Keep away from oils, lotions, and soaking in water, which many Ethiopian opals can absorb. Avoid heat and sudden temperature changes, and wipe with a dry soft cloth.
Is this the exact piece I will receive?
Yes. This listing was photographed individually, and you receive the exact piece shown in the photos.
