The facts
What londonite actually is
Londonite is classified as rhodizite-londonite series, with the composition (Cs,K)Al₄Be₄(B,Be)₁₂O₂₈. It crystallises in the isometric system.
Colour comes from pale yellow to greenish yellow from trace Fe; often colourless, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.693–1.694. Specific gravity around 3.30–3.40. Cleavage: imperfect dodecahedral. Those three numbers separate it from most of what imitates it.
Where londonite comes from
Londonite is produced at Antsongombato, Betafo, Vakinankaratra, Madagascar and Antandrokomby, Madagascar.
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 londonite is treated
Untreated. Hardness 8 makes it wearable in principle, but crystals are small and almost all go to collectors. Rhodizite and londonite are separated only by caesium versus potassium dominance, so most 'rhodizite' on offer needs analysis.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What londonite is confused with
In the trade londonite is most often mistaken for, or substituted by, Rhodizite, Chrysoberyl, Spinel or Diamond.
The separation is rarely a matter of opinion: refractive index 1.693–1.694 and specific gravity 3.30–3.40 settle most of it in a minute, and magnification settles the rest.
What londonite is used for
Demand for londonite comes from mineral collecting and jewellery, 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 or by the carat.
Durability and care
Londonite is 8 on the Mohs scale, with imperfect dodecahedral cleavage.
Hardness is not the whole story. Perfect cleavage means the stone can split cleanly if struck along the wrong plane, whatever its Mohs number, so a protective setting matters more here than the hardness suggests.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What londonite costs
As a guide, londonite trades around Faceted stones 300–1,500 USD/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 londonite treated, and how?
Untreated. Hardness 8 makes it wearable in principle, but crystals are small and almost all go to collectors. Rhodizite and londonite are separated only by caesium versus potassium dominance, so most 'rhodizite' on offer needs analysis.
Where does londonite come from?
Antsongombato, Betafo, Vakinankaratra, Madagascar and Antandrokomby, Madagascar. Origin affects price, so we name the locality rather than the country on every quote.
Is londonite hard enough to wear every day?
With care. It is 8 on the Mohs scale, which is hard enough, but imperfect dodecahedral cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does londonite cost?
Indicatively Faceted stones 300–1,500 USD/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 londonite confused with?
Most often Rhodizite, Chrysoberyl, Spinel and Diamond. A refractive index of 1.693–1.694 and a specific gravity near 3.30–3.40 separate it quickly.
Related stones
Looking for londonite?
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 londonite