The facts
What fire opal actually is
Mineralogically, fire opal is hydrated silica — SiO₂·nH₂O, crystallising in the amorphous system.
The colour is caused by iron oxide. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.37–1.47, and the specific gravity sits near 1.98–2.20; cleavage is none.
Where fire opal comes from
The recognised sources are Querétaro and Jalisco, Mexico, Wollo, Ethiopia and Brazil.
Origin affects price in this material, so we name the locality on every quote rather than the country. "African" or "Asian" tells a buyer nothing.
Is fire opal treated?
None normally. It can craze as it loses water.
That makes disclosure simple: there is nothing to declare. It also means a seller offering a "treated" version of this material is offering something else.
What fire opal is confused with
The usual confusions are Spessartite, Carnelian and Glass.
The separation is rarely a matter of opinion: refractive index 1.37–1.47 and specific gravity 1.98–2.20 settle most of it in a minute, and magnification settles the rest.
What fire opal is used for
Fire opal is bought by jewellery and mineral collecting — and each of those trades wants a different form of the same material.
We quote each application in the unit that trade actually buys in, by the carat or by the specimen.
Durability and care
Hardness 5.5–6.5; cleavage none. That combination decides what it can safely be set into.
With no cleavage plane to worry about, the practical limit is abrasion rather than breakage, and it takes daily wear well.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What fire opal costs
Indicative pricing for fire opal is $10–500/ct.
That is a range, not a quote. Colour, size, clarity, cut and origin move the figure a long way inside it, and the only honest price is one given against a specific stone. Send us what you need and we will price it.
Questions
Is fire opal treated?
None normally. It can craze as it loses water.
Where does fire opal come from?
Querétaro and Jalisco, Mexico, Wollo, Ethiopia and Brazil. Origin affects price, so we name the locality rather than the country on every quote.
Is fire opal hard enough to wear every day?
Yes. At 5.5–6.5 on the Mohs scale with no cleavage plane, it handles daily wear well. The practical limit is gradual abrasion rather than chipping.
How much does fire opal cost?
Indicatively $10–500/ct. Colour, size, clarity and origin move the price a long way within that, so treat it as a range and ask for a quote against a specific stone.
What is fire opal confused with?
Most often Spessartite, Carnelian and Glass. A refractive index of 1.37–1.47 and a specific gravity near 1.98–2.20 separate it quickly.
Related stones
Looking for fire opal?
Tell us the size, the quality and what it is for. We source it, photograph it and quote it — with the locality named.
Ask about fire opal