The facts
What sardonyx actually is
Mineralogically, sardonyx is chalcedony (banded) — SiO₂, crystallising in the trigonal (cryptocrystalline) system.
The colour is caused by alternating white and reddish-brown (iron oxide) bands. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.530–1.539, and the specific gravity sits near 2.58–2.64; cleavage is none.
Where sardonyx comes from
The recognised sources are Ratanpur, Gujarat, India, Idar-Oberstein, Germany (cutting centre) 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.
How sardonyx is treated
Traditionally heated and dyed to sharpen band contrast for cameo and intaglio cutting. The classical cameo material is treated and has been for two millennia.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What sardonyx is confused with
The usual confusions are Dyed agate, Carnelian, Shell cameo and Glass cameo.
The separation is rarely a matter of opinion: refractive index 1.530–1.539 and specific gravity 2.58–2.64 settle most of it in a minute, and magnification settles the rest.
What sardonyx is used for
Sardonyx is bought by jewellery, carving and sculpture, decorative objects 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, by the block or by the piece.
Durability and care
Sardonyx is 6.5–7 on the Mohs scale, with none cleavage.
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 sardonyx costs
Indicative pricing for sardonyx is $1–20/ct; carved cameos priced by workmanship.
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 sardonyx treated, and how?
Traditionally heated and dyed to sharpen band contrast for cameo and intaglio cutting. The classical cameo material is treated and has been for two millennia.
Where does sardonyx come from?
Ratanpur, Gujarat, India, Idar-Oberstein, Germany (cutting centre) and Brazil. Origin affects price, so we name the locality rather than the country on every quote.
Is sardonyx hard enough to wear every day?
Yes. At 6.5–7 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 sardonyx cost?
Indicatively $1–20/ct; carved cameos priced by workmanship. 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 sardonyx confused with?
Most often Dyed agate, Carnelian, Shell cameo and Glass cameo. A refractive index of 1.530–1.539 and a specific gravity near 2.58–2.64 separate it quickly.
What is sardonyx used for besides jewellery?
carving and sculpture, decorative objects and mineral collecting. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for sardonyx?
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 sardonyx