The facts
What cat's Eye Sillimanite actually is
Mineralogically, cat's Eye Sillimanite is sillimanite — Al₂SiO₅, crystallising in the orthorhombic system.
The colour is caused by trace Fe gives grey-blue to greenish; sillimanite is naturally fibrous, so chatoyancy is intrinsic rather than inclusion-driven. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.657–1.680, and the specific gravity sits near 3.23–3.27; cleavage is perfect in one direction.
Where cat's Eye Sillimanite comes from
The recognised sources are Ratnapura, Sri Lanka, Mogok, Myanmar and Idaho, USA.
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 cat's Eye Sillimanite is treated
Untreated. The fibrous habit gives a broad, silky band rather than a knife-sharp eye. Perfect cleavage makes setting delicate.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What cat's Eye Sillimanite is confused with
The usual confusions are Cat's eye quartz, Cat's eye chrysoberyl, Moonstone and Cat's eye enstatite.
The separation is rarely a matter of opinion: refractive index 1.657–1.680 and specific gravity 3.23–3.27 settle most of it in a minute, and magnification settles the rest.
What cat's Eye Sillimanite is used for
Cat's Eye Sillimanite is bought by jewellery 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 or by the specimen.
Durability and care
Hardness 6.5–7.5; cleavage perfect in one direction. That combination decides what it can safely be set into.
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 cat's Eye Sillimanite costs
Indicative pricing for cat's Eye Sillimanite is 30–200 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 cat's Eye Sillimanite treated, and how?
Untreated. The fibrous habit gives a broad, silky band rather than a knife-sharp eye. Perfect cleavage makes setting delicate.
Where does cat's Eye Sillimanite come from?
Ratnapura, Sri Lanka, Mogok, Myanmar and Idaho, USA. Origin affects price, so we name the locality rather than the country on every quote.
Is cat's Eye Sillimanite hard enough to wear every day?
With care. It is 6.5–7.5 on the Mohs scale, which is hard enough, but perfect in one direction cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does cat's Eye Sillimanite cost?
Indicatively 30–200 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 cat's Eye Sillimanite confused with?
Most often Cat's eye quartz, Cat's eye chrysoberyl, Moonstone and Cat's eye enstatite. A refractive index of 1.657–1.680 and a specific gravity near 3.23–3.27 separate it quickly.
Related stones
Looking for cat's eye sillimanite?
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 cat's eye sillimanite