The facts
What cordierite (Technical Ceramic) actually is
Mineralogically, cordierite (Technical Ceramic) is a magnesium aluminosilicate with a near-zero coefficient of thermal expansion, which makes it the standard material for thermal-shock-resistant ceramics - though the technical product is almost always synthesised, not mined — Mg2Al4Si5O18, crystallising in the orthorhombic system.
The colour is caused by fe2+ and Fe3+ intervalence charge transfer gives the blue-violet, with intense pleochroism - blue, grey and pale yellow in three directions, which is why the gem is called dichroite. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.
A refractometer reads 1.522-1.578, and the specific gravity sits near 2.55-2.75; cleavage is distinct in one direction.
Where cordierite (Technical Ceramic) comes from
The recognised sources are Synthetic cordierite bodies are made from talc, kaolin and alumina - the commercial technical route and Natural gem iolite: Ratnapura, Sri Lanka; Anakie, Queensland, Australia; Madagascar; Orissa, India; Tanzania.
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 cordierite (Technical Ceramic) is treated
THE HONEST POINT: kiln shelves, pizza stones, catalytic converter substrates and diesel particulate filters described as 'cordierite' are manufactured ceramic bodies synthesised from talc, clay and alumina - they are not made from mined cordierite, and a site that says otherwise is repeating a common error. Natural cordierite is mined only as gem iolite and as a minor collector mineral. The extreme thermal-shock resistance comes from the near-zero thermal expansion of the crystal structure, which is real and is why the synthetic material dominates honeycomb substrates for vehicle emissions control. Gem iolite is generally untreated - there is no accepted enhancement.
None of this is a problem when it is said out loud. It becomes one the moment it is left out.
What cordierite (Technical Ceramic) is confused with
The usual confusions are Mullite and alumina kiln furniture, Synthetic cordierite (the actual technical material), Tanzanite, sapphire and lolite - iolite is the cheap blue substitute and Silicon carbide kiln shelves.
The separation is rarely a matter of opinion: refractive index 1.522-1.578 and specific gravity 2.55-2.75 settle most of it in a minute, and magnification settles the rest.
What cordierite (Technical Ceramic) is used for
Cordierite (Technical Ceramic) is bought by heavy industry, kitchen and table, jewellery 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 tonne, by the piece or by the carat.
Durability and care
Cordierite (Technical Ceramic) is 7-7.5 on the Mohs scale, with distinct in one direction cleavage.
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 cordierite (Technical Ceramic) costs
Indicative pricing for cordierite (Technical Ceramic) is Technical cordierite ceramics $5-60 per kiln shelf or bakestone; gem iolite $20-150 per carat.
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 cordierite (Technical Ceramic) treated, and how?
THE HONEST POINT: kiln shelves, pizza stones, catalytic converter substrates and diesel particulate filters described as 'cordierite' are manufactured ceramic bodies synthesised from talc, clay and alumina - they are not made from mined cordierite, and a site that says otherwise is repeating a common error. Natural cordierite is mined only as gem iolite and as a minor collector mineral. The extreme thermal-shock resistance comes from the near-zero thermal expansion of the crystal structure, which is real and is why the synthetic material dominates honeycomb substrates for vehicle emissions control. Gem iolite is generally untreated - there is no accepted enhancement.
Where does cordierite (Technical Ceramic) come from?
Synthetic cordierite bodies are made from talc, kaolin and alumina - the commercial technical route and Natural gem iolite: Ratnapura, Sri Lanka; Anakie, Queensland, Australia; Madagascar; Orissa, India; Tanzania. Origin affects price, so we name the locality rather than the country on every quote.
Is cordierite (Technical Ceramic) hard enough to wear every day?
Yes. At 7-7.5 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 cordierite (Technical Ceramic) cost?
Indicatively Technical cordierite ceramics $5-60 per kiln shelf or bakestone; gem iolite $20-150 per carat. 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 cordierite (Technical Ceramic) confused with?
Most often Mullite and alumina kiln furniture, Synthetic cordierite (the actual technical material), Tanzanite, sapphire and lolite - iolite is the cheap blue substitute and Silicon carbide kiln shelves. A refractive index of 1.522-1.578 and a specific gravity near 2.55-2.75 separate it quickly.
What is cordierite (Technical Ceramic) used for besides jewellery?
heavy industry, kitchen and table and mineral collecting. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for cordierite (technical ceramic)?
Tell us the size, the quality and what it is for. We source it, photograph it and quote it — with the locality named.
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