The facts
What anorthoclase actually is
The species behind anorthoclase is feldspar group (alkali), (Na,K)AlSi₃O₈; it forms in the triclinic, pseudo-monoclinic system.
Colourless to pale yellow; sheen from cryptoperthitic exsolution lamellae is responsible for the colour — and the chromophore, not the name, is what decides whether a colour is stable.
On the instruments it reads a refractive index of 1.518–1.534 and a specific gravity of about 2.56–2.62, with perfect basal, good prismatic cleavage.
Where anorthoclase comes from
Commercial material comes from Mount Erebus, Ross Island, Antarctica, Grande Caldeira, Azores, Portugal and Kenya Rift Valley, Kenya.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How anorthoclase is treated
Untreated. Facetable transparent crystals come mainly from Kenyan and Malagasy lavas.
We state the treatment on every stone, including when the honest answer is that it cannot be determined. A treatment disclosed is a fact; a treatment discovered later is a refund.
What anorthoclase is confused with
Watch for Sanidine, Orthoclase and Moonstone — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.518–1.534 and specific gravity 2.56–2.62 settle most of it in a minute, and magnification settles the rest.
What anorthoclase is used for
The trades that buy anorthoclase are mineral collecting and jewellery. They do not want the same thing, and they do not pay in the same unit.
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 basal, good prismatic. 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 anorthoclase costs
Expect roughly 15–100 USD/ct, depending on quality.
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 anorthoclase treated, and how?
Untreated. Facetable transparent crystals come mainly from Kenyan and Malagasy lavas.
Where does anorthoclase come from?
Mount Erebus, Ross Island, Antarctica, Grande Caldeira, Azores, Portugal and Kenya Rift Valley, Kenya. Origin affects price, so we name the locality rather than the country on every quote.
Is anorthoclase hard enough to wear every day?
With care. It is 6–6.5 on the Mohs scale, which is hard enough, but perfect basal, good prismatic cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does anorthoclase cost?
Indicatively 15–100 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 anorthoclase confused with?
Most often Sanidine, Orthoclase and Moonstone. A refractive index of 1.518–1.534 and a specific gravity near 2.56–2.62 separate it quickly.
Related stones
Looking for anorthoclase?
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 anorthoclase