The facts
What prehnite actually is
Mineralogically, prehnite is prehnite — Ca₂Al₂Si₃O₁₀(OH)₂, crystallising in the orthorhombic system.
The colour is caused by fe²⁺ and Fe³⁺ — the relative content and site occupancy of the two drive the yellow-green colour and its change on heating. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.611–1.673, and the specific gravity sits near 2.80–2.95; cleavage is distinct {001}.
Where prehnite comes from
The recognised sources are Wave Hill Station, Northern Territory, Australia, Jeffrey Mine, Asbestos, Quebec, Canada, Bou-Arfa, Morocco, Fairfax Quarry, Centreville, Virginia, USA and Mali.
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 prehnite is treated
Generally untreated. Sold as translucent yellow-green cabochons with a characteristic cloudy, botryoidal internal structure; faceted transparent material from Australia and Mali is scarcer. Often confused with jade and with grossular in bead form.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What prehnite is confused with
The usual confusions are Jadeite, Grossular, Chrysoprase, Serpentine and Green opal.
The separation is rarely a matter of opinion: refractive index 1.611–1.673 and specific gravity 2.80–2.95 settle most of it in a minute, and magnification settles the rest.
What prehnite is used for
Prehnite is bought by jewellery, carving and sculpture, decorative objects and 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 carat, by the block or by the piece.
Durability and care
Hardness 6–6.5; cleavage distinct {001}. 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 prehnite costs
Indicative pricing for prehnite is $2–40/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 prehnite treated, and how?
Generally untreated. Sold as translucent yellow-green cabochons with a characteristic cloudy, botryoidal internal structure; faceted transparent material from Australia and Mali is scarcer. Often confused with jade and with grossular in bead form.
Where does prehnite come from?
Wave Hill Station, Northern Territory, Australia, Jeffrey Mine, Asbestos, Quebec, Canada, Bou-Arfa, Morocco, Fairfax Quarry, Centreville, Virginia, USA and Mali. Origin affects price, so we name the locality rather than the country on every quote.
Is prehnite hard enough to wear every day?
Yes. At 6–6.5 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 prehnite cost?
Indicatively $2–40/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 prehnite confused with?
Most often Jadeite, Grossular, Chrysoprase, Serpentine and Green opal. A refractive index of 1.611–1.673 and a specific gravity near 2.80–2.95 separate it quickly.
What is prehnite used for besides jewellery?
carving and sculpture, decorative objects and mineral collecting. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for prehnite?
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 prehnite