The facts
What binghamite actually is
Mineralogically, binghamite is chalcedony with goethite and hematite fibres — SiO₂ with FeO(OH) and Fe₂O₃, crystallising in the cryptocrystalline aggregate system.
The colour is caused by iron oxide fibres give red and gold; the silky chatoyancy is reflection off parallel goethite needles. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.530–1.543, and the specific gravity sits near 2.55–2.70; cleavage is none.
Where binghamite comes from
The recognised sources are Cuyuna Iron Range, Crow Wing County, Minnesota, USA.
That is the whole list. A single source makes supply fragile and makes any claim of a second origin worth questioning.
How binghamite is treated
Untreated. The Cuyuna mines closed decades ago, so all material is old stock. Binghamite and silkstone were originally distinguished by fibre length, but the terms are now used interchangeably.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What binghamite is confused with
The usual confusions are Tiger's eye, Tiger iron, Pietersite and Marra Mamba.
The separation is rarely a matter of opinion: refractive index 1.530–1.543 and specific gravity 2.55–2.70 settle most of it in a minute, and magnification settles the rest.
What binghamite is used for
Binghamite is bought by jewellery, mineral collecting and decorative objects — and each of those trades wants a different form of the same material.
We quote each application in the unit that trade actually buys in, by the carat, by the specimen or by the piece.
Durability and care
Binghamite is 6.5–7 on the Mohs scale, with none cleavage.
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 binghamite costs
Indicative pricing for binghamite is Cabochons 30–200 USD; rough scarce.
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 binghamite treated, and how?
Untreated. The Cuyuna mines closed decades ago, so all material is old stock. Binghamite and silkstone were originally distinguished by fibre length, but the terms are now used interchangeably.
Where does binghamite come from?
Cuyuna Iron Range, Crow Wing County, Minnesota, USA. That is the only commercial source.
Is binghamite hard enough to wear every day?
Yes. At 6.5–7 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 binghamite cost?
Indicatively Cabochons 30–200 USD; rough scarce. 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 binghamite confused with?
Most often Tiger's eye, Tiger iron, Pietersite and Marra Mamba. A refractive index of 1.530–1.543 and a specific gravity near 2.55–2.70 separate it quickly.
What is binghamite used for besides jewellery?
mineral collecting and decorative objects. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for binghamite?
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 binghamite