The facts
What gahnite actually is
The species behind gahnite is spinel group, ZnAl₂O₄; it forms in the cubic system.
Fe²⁺ and Fe³⁺ giving dark bluish-green to near-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 1.790–1.820 and a specific gravity of about 4.40–4.62, with none; imperfect octahedral parting cleavage.
Where gahnite comes from
Commercial material comes from Nordmark and Falun, Sweden, Bodenmais, Bavaria, Germany and Broken Hill, New South Wales, Australia.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How gahnite is treated
Untreated. Almost always too dark to face, so it is a specimen and curiosity stone; transparent gem material is genuinely rare.
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 gahnite is confused with
Watch for Dark spinel, Almandine garnet and Magnetite — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.790–1.820 and specific gravity 4.40–4.62 settle most of it in a minute, and magnification settles the rest.
What gahnite is used for
The trades that buy gahnite 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
Gahnite is 7.5–8 on the Mohs scale, with none; imperfect octahedral parting 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 gahnite costs
Expect roughly Crystals on matrix $30–$500; faceted stones $100–$400/ct and rarely over 2 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 gahnite treated, and how?
Untreated. Almost always too dark to face, so it is a specimen and curiosity stone; transparent gem material is genuinely rare.
Where does gahnite come from?
Nordmark and Falun, Sweden, Bodenmais, Bavaria, Germany and Broken Hill, New South Wales, Australia. Origin affects price, so we name the locality rather than the country on every quote.
Is gahnite hard enough to wear every day?
With care. It is 7.5–8 on the Mohs scale, which is hard enough, but none; imperfect octahedral parting cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does gahnite cost?
Indicatively Crystals on matrix $30–$500; faceted stones $100–$400/ct and rarely over 2 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 gahnite confused with?
Most often Dark spinel, Almandine garnet and Magnetite. A refractive index of 1.790–1.820 and a specific gravity near 4.40–4.62 separate it quickly.
Related stones
Looking for gahnite?
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 gahnite