The facts
What ettringite actually is
Ettringite is classified as ettringite, with the composition Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O. It crystallises in the hexagonal system.
Colour comes from traces of Mn giving bright canary to golden yellow; colourless when pure, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.464–1.491. Specific gravity around 1.77–1.80. Cleavage: perfect {1010}. Those three numbers separate it from most of what imitates it.
Where ettringite comes from
Ettringite is produced at N'Chwaning II Mine, Kalahari Manganese Field, South Africa, Ettringen, Eifel, Germany (type locality) and Scawt Hill, County Antrim, Northern Ireland.
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 ettringite is treated
Untreated, but ettringite dehydrates and goes chalky white in dry air, so specimens are usually kept in sealed humidified containers. One of the lowest-density gem-associated minerals at under 1.8. Also a cement hydration product.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What ettringite is confused with
In the trade ettringite is most often mistaken for, or substituted by, Sturmanite, Sulphur, Wulfenite or Calcite.
The separation is rarely a matter of opinion: refractive index 1.464–1.491 and specific gravity 1.77–1.80 settle most of it in a minute, and magnification settles the rest.
What ettringite is used for
Demand for ettringite comes from mineral collecting, 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.
Durability and care
Hardness 2–2.5; cleavage perfect {1010}. That combination decides what it can safely be set into.
Below about 5.5 a stone will be scratched by ordinary household dust, which is largely quartz. That does not make it unusable — it makes it a pendant, an earring or an object rather than a ring worn every day.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What ettringite costs
As a guide, ettringite trades around N'Chwaning specimens $80–$5,000.
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 ettringite treated, and how?
Untreated, but ettringite dehydrates and goes chalky white in dry air, so specimens are usually kept in sealed humidified containers. One of the lowest-density gem-associated minerals at under 1.8. Also a cement hydration product.
Where does ettringite come from?
N'Chwaning II Mine, Kalahari Manganese Field, South Africa, Ettringen, Eifel, Germany (type locality) and Scawt Hill, County Antrim, Northern Ireland. Origin affects price, so we name the locality rather than the country on every quote.
Is ettringite hard enough to wear every day?
Not really. At 2–2.5 on the Mohs scale it is softer than the quartz dust in ordinary household dirt, so it scratches with wear. It suits pendants, earrings and objects better than a daily ring.
How much does ettringite cost?
Indicatively N'Chwaning specimens $80–$5,000. 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 ettringite confused with?
Most often Sturmanite, Sulphur, Wulfenite and Calcite. A refractive index of 1.464–1.491 and a specific gravity near 1.77–1.80 separate it quickly.
Related stones
Looking for ettringite?
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 ettringite