The facts
What thunder Egg actually is
Thunder Egg is classified as rhyolite nodule with a chalcedony or agate core, with the composition SiO₂ core in a rhyolitic shell. It crystallises in the cryptocrystalline core in volcanic matrix system.
Colour comes from iron oxides give the reds and browns of both shell and core; core colour varies with the infilling silica generation, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.530–1.539 (core). Specific gravity around 2.4–2.6. Cleavage: none. Those three numbers separate it from most of what imitates it.
Where thunder Egg comes from
Thunder Egg is produced at Richardson Ranch, Jefferson County, Oregon, USA, Succor Creek, Oregon, USA and Chihuahua, Mexico.
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 thunder Egg is treated
Untreated. Sold whole or sawn in half; the Oregon state rock. Cheap imports are sometimes dyed in the core, which shows as unnaturally even blue or magenta.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What thunder Egg is confused with
In the trade thunder Egg is most often mistaken for, or substituted by, Geode, Agate nodule or Dyed geode slices.
The separation is rarely a matter of opinion: refractive index 1.530–1.539 (core) and specific gravity 2.4–2.6 settle most of it in a minute, and magnification settles the rest.
What thunder Egg is used for
Demand for thunder Egg comes from 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 specimen, by the piece or by the square metre.
Durability and care
Thunder Egg is 6.5–7 core; 6 shell 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 thunder Egg costs
As a guide, thunder Egg trades around 5–60 USD per sawn pair; exceptional patterns far more.
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 thunder Egg treated, and how?
Untreated. Sold whole or sawn in half; the Oregon state rock. Cheap imports are sometimes dyed in the core, which shows as unnaturally even blue or magenta.
Where does thunder Egg come from?
Richardson Ranch, Jefferson County, Oregon, USA, Succor Creek, Oregon, USA and Chihuahua, Mexico. Origin affects price, so we name the locality rather than the country on every quote.
Is thunder Egg hard enough to wear every day?
Yes. At 6.5–7 core; 6 shell 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 thunder Egg cost?
Indicatively 5–60 USD per sawn pair; exceptional patterns far more. 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 thunder Egg confused with?
Most often Geode, Agate nodule and Dyed geode slices. A refractive index of 1.530–1.539 (core) and a specific gravity near 2.4–2.6 separate it quickly.
What is thunder Egg 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 thunder egg?
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 thunder egg