The facts
What neptunite actually is
Mineralogically, neptunite is neptunite — KNa₂Li(Fe²⁺,Mn²⁺,Mg)₂Ti₂Si₈O₂₄, crystallising in the monoclinic system.
The colour is caused by fe²⁺–Ti⁴⁺ intervalence charge transfer, producing an intense band at 415–460 nm; black in mass, deep red-brown in thin fragments. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.692–1.734, and the specific gravity sits near 3.19–3.23; cleavage is perfect {110}; brittle, conchoidal fracture.
Where neptunite comes from
The recognised sources are Benitoite Gem Mine, San Benito County, California, USA, Narssârssuk and Ilímaussaq, Greenland, Khibiny and Lovozero massifs, Kola Peninsula, Russia and Mont Saint-Hilaire, Quebec, Canada.
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 neptunite is treated
Untreated. The lustrous black prisms in white natrolite alongside blue benitoite are among the most recognisable mineral specimens in the world, and that association is where its value sits. Piezoelectric. Almost never cut.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What neptunite is confused with
The usual confusions are Aegirine, Schorl, Arfvedsonite and Black spinel.
The separation is rarely a matter of opinion: refractive index 1.692–1.734 and specific gravity 3.19–3.23 settle most of it in a minute, and magnification settles the rest.
What neptunite is used for
Neptunite is bought by 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 specimen or by the piece.
Durability and care
Neptunite is 5–6 on the Mohs scale, with perfect {110}; brittle, conchoidal fracture cleavage.
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 neptunite costs
Indicative pricing for neptunite is Specimen pricing.
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 neptunite treated, and how?
Untreated. The lustrous black prisms in white natrolite alongside blue benitoite are among the most recognisable mineral specimens in the world, and that association is where its value sits. Piezoelectric. Almost never cut.
Where does neptunite come from?
Benitoite Gem Mine, San Benito County, California, USA, Narssârssuk and Ilímaussaq, Greenland, Khibiny and Lovozero massifs, Kola Peninsula, Russia and Mont Saint-Hilaire, Quebec, Canada. Origin affects price, so we name the locality rather than the country on every quote.
Is neptunite hard enough to wear every day?
Not really. At 5–6 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 neptunite cost?
Indicatively Specimen pricing. 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 neptunite confused with?
Most often Aegirine, Schorl, Arfvedsonite and Black spinel. A refractive index of 1.692–1.734 and a specific gravity near 3.19–3.23 separate it quickly.
Related stones
Looking for neptunite?
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 neptunite