The facts
What agatized Coral actually is
Agatized Coral is classified as oligocene-Miocene scleractinian coral colonies in which the aragonite skeleton has been replaced by chalcedony - a fossil, and silica, not carbonate, with the composition SiO2 chalcedony after CaCO3. It crystallises in the aggregate (cryptocrystalline trigonal quartz) system.
Colour comes from iron oxides and organic residues give tan, grey and pink tones, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.53-1.54 (spot). Specific gravity around 2.55-2.65. Cleavage: none. Those three numbers separate it from most of what imitates it.
Where agatized Coral comes from
Agatized Coral is produced at Tampa Bay, Ballast Point and the Withlacoochee River, Florida, USA (Florida state stone), Suwannee River, Florida, USA, Sulawesi and Java, Indonesia and Sichuan and Guangxi, China.
The locality is part of the description, not a footnote — two stones of the same weight from two of these places are not the same stone.
How agatized Coral is treated
Normally untreated; some Indonesian material is dyed to strengthen contrast. Not CITES - fossilised, not a living coral product, though customs officers occasionally confuse the two and asking for a fossil declaration is prudent. Florida collecting requires a state fossil permit on state lands, and Ballast Point is now closed to collecting.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What agatized Coral is confused with
In the trade agatized Coral is most often mistaken for, or substituted by, Ordinary jasper and agate, Dyed Indonesian material or Modern coral (which is soft and effervesces in acid - this does not).
The separation is rarely a matter of opinion: refractive index 1.53-1.54 (spot) and specific gravity 2.55-2.65 settle most of it in a minute, and magnification settles the rest.
What agatized Coral is used for
Demand for agatized Coral comes from jewellery, mineral collecting, decorative objects and architecture and interiors, which is why one price per carat never covers it.
We quote each application in the unit that trade actually buys in, by the carat, by the specimen or by the piece.
Durability and care
Hardness 6.5-7; 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 agatized Coral costs
As a guide, agatized Coral trades around $1-15 per carat cut; display slabs and heads $30-400 each.
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 agatized Coral treated, and how?
Normally untreated; some Indonesian material is dyed to strengthen contrast. Not CITES - fossilised, not a living coral product, though customs officers occasionally confuse the two and asking for a fossil declaration is prudent. Florida collecting requires a state fossil permit on state lands, and Ballast Point is now closed to collecting.
Where does agatized Coral come from?
Tampa Bay, Ballast Point and the Withlacoochee River, Florida, USA (Florida state stone), Suwannee River, Florida, USA, Sulawesi and Java, Indonesia and Sichuan and Guangxi, China. Origin affects price, so we name the locality rather than the country on every quote.
Is agatized Coral 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 agatized Coral cost?
Indicatively $1-15 per carat cut; display slabs and heads $30-400 each. 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 agatized Coral confused with?
Most often Ordinary jasper and agate, Dyed Indonesian material and Modern coral (which is soft and effervesces in acid - this does not). A refractive index of 1.53-1.54 (spot) and a specific gravity near 2.55-2.65 separate it quickly.
What is agatized Coral used for besides jewellery?
mineral collecting, decorative objects and architecture and interiors. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for agatized coral?
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 agatized coral