The facts
What bournonite actually is
Mineralogically, bournonite is bournonite — PbCuSbS₃, crystallising in the orthorhombic system.
The colour is caused by metallic steel-grey to black; the interest is the cyclic twinning that produces cogwheel-shaped crystals. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer gives nothing, because the material is opaque, and the specific gravity sits near 5.7–5.9; cleavage is imperfect {010}.
Where bournonite comes from
The recognised sources are Herodsfoot Mine, Liskeard, Cornwall, England, Yaogangxian, Hunan, China, Baia Sprie, Romania and Pribram, Czech Republic.
Origin affects price in this material, so we name the locality on every quote rather than the country. "African" or "Asian" tells a buyer nothing.
How bournonite is treated
Untreated. Herodsfoot cogwheel twins from the 1860s–70s remain the finest ever found and are museum pieces; modern Chinese material is excellent and much more affordable.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What bournonite is confused with
The usual confusions are Galena, Stibnite, Tetrahedrite and Jamesonite.
Because the material is opaque, refractive index is no help. Specific gravity around 5.7–5.9, hardness of 2.5–3, streak and magnification do the work instead.
What bournonite is used for
Bournonite is bought by mineral collecting — 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 specimen.
Durability and care
Hardness 2.5–3; cleavage imperfect {010}. 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 bournonite costs
Indicative pricing for bournonite is Specimens $40–$5,000; classic Cornish cogwheels far higher.
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 bournonite treated, and how?
Untreated. Herodsfoot cogwheel twins from the 1860s–70s remain the finest ever found and are museum pieces; modern Chinese material is excellent and much more affordable.
Where does bournonite come from?
Herodsfoot Mine, Liskeard, Cornwall, England, Yaogangxian, Hunan, China, Baia Sprie, Romania and Pribram, Czech Republic. Origin affects price, so we name the locality rather than the country on every quote.
Is bournonite hard enough to wear every day?
Not really. At 2.5–3 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 bournonite cost?
Indicatively Specimens $40–$5,000; classic Cornish cogwheels far higher. 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 bournonite confused with?
Most often Galena, Stibnite, Tetrahedrite and Jamesonite. Since the material is opaque, separation relies on specific gravity near 5.7–5.9, hardness and magnification.
Related stones
Looking for bournonite?
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 bournonite