The facts
What diallage actually is
The species behind diallage is pyroxene (textural variety), (Ca,Mg,Fe)₂Si₂O₆; it forms in the monoclinic system.
Fe²⁺ gives the green-brown; the metallic schiller comes from oriented exsolution lamellae and inclusions on the parting planes 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 1.67–1.75 and a specific gravity of about 3.2–3.4, with prominent parting parallel to the front pinacoid, which defines the variety cleavage.
Where diallage comes from
Commercial material comes from Val d'Aosta, Italy and Corsica, France.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How diallage is treated
Untreated. An old rock-forming term that survives in the lapidary trade rather than in current mineral nomenclature; use it descriptively.
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 diallage is confused with
Watch for Bronzite, Hypersthene and Enstatite — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.67–1.75 and specific gravity 3.2–3.4 settle most of it in a minute, and magnification settles the rest.
What diallage is used for
The trades that buy diallage are mineral collecting and carving and sculpture. 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 block.
Durability and care
Hardness 5–6; cleavage prominent parting parallel to the front pinacoid, which defines the variety. That combination decides what it can safely be set into.
Below about 5.5 a stone will be scratched by ordinary household dust, which is largely quartz. That does not make it unusable — it makes it a pendant, an earring or an object rather than a ring worn every day.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What diallage costs
Expect roughly Cabochons 10–40 USD, 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 diallage treated, and how?
Untreated. An old rock-forming term that survives in the lapidary trade rather than in current mineral nomenclature; use it descriptively.
Where does diallage come from?
Val d'Aosta, Italy and Corsica, France. Origin affects price, so we name the locality rather than the country on every quote.
Is diallage hard enough to wear every day?
Not really. At 5–6 on the Mohs scale it is softer than the quartz dust in ordinary household dirt, so it scratches with wear. It suits pendants, earrings and objects better than a daily ring.
How much does diallage cost?
Indicatively Cabochons 10–40 USD. 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 diallage confused with?
Most often Bronzite, Hypersthene and Enstatite. A refractive index of 1.67–1.75 and a specific gravity near 3.2–3.4 separate it quickly.
Related stones
Looking for diallage?
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 diallage