The facts
What anorthite actually is
The species behind anorthite is feldspar group (plagioclase), CaAl₂Si₂O₈; it forms in the triclinic system.
Normally colourless to white; reddish tints from iron oxide inclusions 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 1.575–1.588 and a specific gravity of about 2.74–2.77, with perfect basal and good prismatic cleavage.
Where anorthite comes from
Commercial material comes from Miyake-jima, Izu Islands, Japan, Vesuvius, Campania, Italy and Grass Valley, California, USA.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How anorthite is treated
No treatments in use. Clean facetable material is scarce and strictly a collector item.
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 anorthite is confused with
Watch for Bytownite, Labradorite and Quartz — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.575–1.588 and specific gravity 2.74–2.77 settle most of it in a minute, and magnification settles the rest.
What anorthite is used for
The trades that buy anorthite are mineral collecting. 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.
Durability and care
Anorthite is 6–6.5 on the Mohs scale, with perfect basal and good prismatic 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 anorthite costs
Expect roughly Faceted stones typically 20–150 USD/ct because of rarity, not beauty, 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 anorthite treated, and how?
No treatments in use. Clean facetable material is scarce and strictly a collector item.
Where does anorthite come from?
Miyake-jima, Izu Islands, Japan, Vesuvius, Campania, Italy and Grass Valley, California, USA. Origin affects price, so we name the locality rather than the country on every quote.
Is anorthite hard enough to wear every day?
With care. It is 6–6.5 on the Mohs scale, which is hard enough, but perfect basal and good prismatic cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does anorthite cost?
Indicatively Faceted stones typically 20–150 USD/ct because of rarity, not beauty. 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 anorthite confused with?
Most often Bytownite, Labradorite and Quartz. A refractive index of 1.575–1.588 and a specific gravity near 2.74–2.77 separate it quickly.
Related stones
Looking for anorthite?
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 anorthite