The facts
What orthoclase actually is
Orthoclase is classified as orthoclase (feldspar group), with the composition KAlSi₃O₈. It crystallises in the monoclinic system.
Colour comes from fe³⁺ substituting for Al gives the yellow, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.518–1.526. Specific gravity around 2.55–2.59. Cleavage: perfect {001}, good {010} — two cleavages near 90°. Those three numbers separate it from most of what imitates it.
Where orthoclase comes from
Orthoclase is produced at Itrongay, Fianarantsoa, Madagascar and Fianarantsoa Province, 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 orthoclase is treated
Untreated. Fragile in wear because of the two good cleavages; a collector and connoisseur stone rather than a ring stone.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What orthoclase is confused with
In the trade orthoclase is most often mistaken for, or substituted by, Citrine, Yellow beryl, Yellow scapolite or Danburite.
The separation is rarely a matter of opinion: refractive index 1.518–1.526 and specific gravity 2.55–2.59 settle most of it in a minute, and magnification settles the rest.
What orthoclase is used for
Demand for orthoclase comes from jewellery and 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 carat or by the specimen.
Durability and care
Orthoclase is 6–6.5 on the Mohs scale, with perfect {001}, good {010} — two cleavages near 90° 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 orthoclase costs
As a guide, orthoclase trades around $20–150/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 orthoclase treated, and how?
Untreated. Fragile in wear because of the two good cleavages; a collector and connoisseur stone rather than a ring stone.
Where does orthoclase come from?
Itrongay, Fianarantsoa, Madagascar and Fianarantsoa Province, Madagascar. Origin affects price, so we name the locality rather than the country on every quote.
Is orthoclase 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} — two cleavages near 90° cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does orthoclase cost?
Indicatively $20–150/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 orthoclase confused with?
Most often Citrine, Yellow beryl, Yellow scapolite and Danburite. A refractive index of 1.518–1.526 and a specific gravity near 2.55–2.59 separate it quickly.
Related stones
Looking for orthoclase?
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 orthoclase