The facts
What colemanite actually is
Mineralogically, colemanite is colemanite — CaB₃O₄(OH)₃·H₂O, crystallising in the monoclinic system.
The colour is caused by colourless to milky white or pale yellow; impurity-driven. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.586–1.614, and the specific gravity sits near 2.42; cleavage is perfect {010}, distinct {001}.
Where colemanite comes from
The recognised sources are Boron (Kramer district) and Death Valley, California, USA, Bigadiç and Emet, Balıkesir/Kütahya, Turkey and Billie Mine, Death Valley, California, USA.
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 colemanite is treated
Untreated. Water-soluble only very slowly, so it survives handling better than ulexite or borax; faceted colemanite is a soft colourless collector stone. The principal boron ore alongside borax and ulexite.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What colemanite is confused with
The usual confusions are Calcite, Danburite, Datolite, Quartz and Gypsum.
The separation is rarely a matter of opinion: refractive index 1.586–1.614 and specific gravity 2.42 settle most of it in a minute, and magnification settles the rest.
What colemanite is used for
Colemanite is bought by mineral collecting and heavy industry — 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 or by the tonne.
Durability and care
Hardness 4.5; cleavage perfect {010}, distinct {001}. 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 colemanite costs
Indicative pricing for colemanite is Specimens $20–$800; faceted stones $30–$120/ct.
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 colemanite treated, and how?
Untreated. Water-soluble only very slowly, so it survives handling better than ulexite or borax; faceted colemanite is a soft colourless collector stone. The principal boron ore alongside borax and ulexite.
Where does colemanite come from?
Boron (Kramer district) and Death Valley, California, USA, Bigadiç and Emet, Balıkesir/Kütahya, Turkey and Billie Mine, Death Valley, California, USA. Origin affects price, so we name the locality rather than the country on every quote.
Is colemanite hard enough to wear every day?
Not really. At 4.5 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 colemanite cost?
Indicatively Specimens $20–$800; faceted stones $30–$120/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 colemanite confused with?
Most often Calcite, Danburite, Datolite, Quartz and Gypsum. A refractive index of 1.586–1.614 and a specific gravity near 2.42 separate it quickly.
Related stones
Looking for colemanite?
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 colemanite