The facts
What cobalt spinel actually is
Cobalt spinel is classified as spinel, with the composition MgAl₂O₄. It crystallises in the cubic system.
Colour comes from cobalt, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.712–1.736. Specific gravity around 3.58–3.61. Cleavage: none. Those three numbers separate it from most of what imitates it.
Where cobalt spinel comes from
Cobalt spinel is produced at Luc Yen, Vietnam, Mahenge, Tanzania and Sri Lanka.
The locality is part of the description, not a footnote — two stones of the same weight from two of these places are not the same stone.
Is cobalt spinel treated?
None normally. The LMHC issues a dedicated information sheet on the name.
That makes disclosure simple: there is nothing to declare. It also means a seller offering a "treated" version of this material is offering something else.
What cobalt spinel is confused with
In the trade cobalt spinel is most often mistaken for, or substituted by, Blue spinel coloured by iron, Synthetic spinel or Sapphire.
The separation is rarely a matter of opinion: refractive index 1.712–1.736 and specific gravity 3.58–3.61 settle most of it in a minute, and magnification settles the rest.
What cobalt spinel is used for
Demand for cobalt spinel comes from mineral collecting and jewellery, which is why one price per carat never covers it.
We quote each application in the unit that trade actually buys in, by the specimen or by the carat.
Durability and care
Hardness 8; cleavage none. 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 cobalt spinel costs
As a guide, cobalt spinel trades around $1,000–30,000/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 cobalt spinel treated?
None normally. The LMHC issues a dedicated information sheet on the name.
Where does cobalt spinel come from?
Luc Yen, Vietnam, Mahenge, Tanzania and Sri Lanka. Origin affects price, so we name the locality rather than the country on every quote.
Is cobalt spinel hard enough to wear every day?
Yes. At 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 cobalt spinel cost?
Indicatively $1,000–30,000/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 cobalt spinel confused with?
Most often Blue spinel coloured by iron, Synthetic spinel and Sapphire. A refractive index of 1.712–1.736 and a specific gravity near 3.58–3.61 separate it quickly.
Related stones
Looking for cobalt spinel?
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 cobalt spinel