The facts
What hercynite actually is
The species behind hercynite is spinel group, Fe²⁺Al₂O₄; it forms in the isometric system.
Fe²⁺ gives dark blue-green to black 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 1.800–1.835 and a specific gravity of about 4.30–4.40, with none; conchoidal fracture cleavage.
Where hercynite comes from
Commercial material comes from Dolon paleovalley, Naryn Region, Kyrgyzstan, Bohemia, Czech Republic and Mount Vesuvius, Campania, Italy.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How hercynite is treated
Untreated. Nearly opaque, so it is cut only for spinel-series completeness. Also produced synthetically as a refractory.
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 hercynite is confused with
Watch for Ceylonite, Gahnite, Magnetite and Black spinel — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.800–1.835 and specific gravity 4.30–4.40 settle most of it in a minute, and magnification settles the rest.
What hercynite is used for
The trades that buy hercynite are mineral collecting and heavy industry. 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 tonne.
Durability and care
Hardness 7.5–8; cleavage none; conchoidal fracture. That combination decides what it can safely be set into.
With no cleavage plane to worry about, the practical limit is abrasion rather than breakage, and it takes daily wear well.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What hercynite costs
Expect roughly Faceted stones 30–150 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 hercynite treated, and how?
Untreated. Nearly opaque, so it is cut only for spinel-series completeness. Also produced synthetically as a refractory.
Where does hercynite come from?
Dolon paleovalley, Naryn Region, Kyrgyzstan, Bohemia, Czech Republic and Mount Vesuvius, Campania, Italy. Origin affects price, so we name the locality rather than the country on every quote.
Is hercynite hard enough to wear every day?
Yes. At 7.5–8 on the Mohs scale with no cleavage plane, it handles daily wear well. The practical limit is gradual abrasion rather than chipping.
How much does hercynite cost?
Indicatively Faceted stones 30–150 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 hercynite confused with?
Most often Ceylonite, Gahnite, Magnetite and Black spinel. A refractive index of 1.800–1.835 and a specific gravity near 4.30–4.40 separate it quickly.
Related stones
Looking for hercynite?
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 hercynite