The facts
What sanidine actually is
Mineralogically, sanidine is sanidine (feldspar group) — (K,Na)AlSi₃O₈, crystallising in the monoclinic system.
The colour is caused by usually colourless; smoky and yellow tints from Fe and colour centres. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.518–1.524, and the specific gravity sits near 2.56–2.62; cleavage is perfect {001}, good {010}.
Where sanidine comes from
The recognised sources are Eifel, Germany, Itrongay, Madagascar and Volcanic fields of Mexico.
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 sanidine is treated
Untreated. A collector feldspar; high-temperature polymorph of K-feldspar, often with schiller from included inclusions.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What sanidine is confused with
The usual confusions are Orthoclase, Moonstone and Colourless quartz.
The separation is rarely a matter of opinion: refractive index 1.518–1.524 and specific gravity 2.56–2.62 settle most of it in a minute, and magnification settles the rest.
What sanidine is used for
Sanidine is bought by mineral collecting and jewellery — 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 specimen or by the carat.
Durability and care
Hardness 6–6.5; cleavage perfect {001}, good {010}. 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 sanidine costs
Indicative pricing for sanidine is $5–50/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 sanidine treated, and how?
Untreated. A collector feldspar; high-temperature polymorph of K-feldspar, often with schiller from included inclusions.
Where does sanidine come from?
Eifel, Germany, Itrongay, Madagascar and Volcanic fields of Mexico. Origin affects price, so we name the locality rather than the country on every quote.
Is sanidine hard enough to wear every day?
With care. It is 6–6.5 on the Mohs scale, which is hard enough, but perfect {001}, good {010} cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does sanidine cost?
Indicatively $5–50/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 sanidine confused with?
Most often Orthoclase, Moonstone and Colourless quartz. A refractive index of 1.518–1.524 and a specific gravity near 2.56–2.62 separate it quickly.
Related stones
Looking for sanidine?
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 sanidine