The facts
What vermiculite actually is
Vermiculite is classified as a hydrated magnesium-aluminium sheet silicate, an alteration product of biotite and phlogopite, which exfoliates dramatically on rapid heating as interlayer water flashes to steam, with the composition (Mg,Fe,Al)3(Al,Si)4O10(OH)2.4H2O. It crystallises in the monoclinic system.
Colour comes from bronze-gold to brown before expansion, pale gold-grey after, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.52-1.58. Specific gravity around 2.4-2.7 unexpanded; 0.06-0.16 bulk density once exfoliated. Cleavage: perfect basal. Those three numbers separate it from most of what imitates it.
Where vermiculite comes from
Vermiculite is produced at Palabora (Phalaborwa), Limpopo, South Africa - the largest producer, Brazil (Goias, Bahia, Paraiba), Hebei and Xinjiang, China, Libby, Montana, USA - closed in 1990 and Uganda and Zimbabwe.
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.
How vermiculite is treated
Exfoliated by rapid heating to 800-1,000 C, which expands it up to about 15 times. Uses: loose-fill and board insulation, horticultural growing medium, lightweight concrete and plaster, fireproofing, packaging and absorbents. THE LIBBY DISASTER IS THE DEFINING FACT: the Libby, Montana mine supplied roughly 70% of world vermiculite for decades and its ore was contaminated with amphibole (winchite-richterite) asbestos, causing hundreds of deaths and thousands of asbestos-related illnesses among workers and residents; the site became an EPA public-health emergency and Zonolite attic insulation in millions of homes remains a live remediation issue. Current commercial vermiculite from Palabora, Brazil and China is tested and regarded as asbestos-free, but any pre-1990 vermiculite insulation should be treated as suspect.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What vermiculite is confused with
In the trade vermiculite is most often mistaken for, or substituted by, Perlite (the other expanded lightweight aggregate), Mica (the parent mineral) or Exfoliated clays.
The separation is rarely a matter of opinion: refractive index 1.52-1.58 and specific gravity 2.4-2.7 unexpanded; 0.06-0.16 bulk density once exfoliated settle most of it in a minute, and magnification settles the rest.
What vermiculite is used for
Demand for vermiculite comes from heavy industry, architecture and interiors and filtration, which is why one price per carat never covers it.
We quote each application in the unit that trade actually buys in, by the tonne or by the square metre.
Durability and care
Hardness 1.5-2; cleavage perfect basal. 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 vermiculite costs
As a guide, vermiculite trades around $150-500 per tonne unexpanded concentrate depending on grade and flake size.
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 vermiculite treated, and how?
Exfoliated by rapid heating to 800-1,000 C, which expands it up to about 15 times. Uses: loose-fill and board insulation, horticultural growing medium, lightweight concrete and plaster, fireproofing, packaging and absorbents. THE LIBBY DISASTER IS THE DEFINING FACT: the Libby, Montana mine supplied roughly 70% of world vermiculite for decades and its ore was contaminated with amphibole (winchite-richterite) asbestos, causing hundreds of deaths and thousands of asbestos-related illnesses among workers and residents; the site became an EPA public-health emergency and Zonolite attic insulation in millions of homes remains a live remediation issue. Current commercial vermiculite from Palabora, Brazil and China is tested and regarded as asbestos-free, but any pre-1990 vermiculite insulation should be treated as suspect.
Where does vermiculite come from?
Palabora (Phalaborwa), Limpopo, South Africa - the largest producer, Brazil (Goias, Bahia, Paraiba), Hebei and Xinjiang, China, Libby, Montana, USA - closed in 1990 and Uganda and Zimbabwe. Origin affects price, so we name the locality rather than the country on every quote.
Is vermiculite hard enough to wear every day?
Not really. At 1.5-2 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 vermiculite cost?
Indicatively $150-500 per tonne unexpanded concentrate depending on grade and flake size. 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 vermiculite confused with?
Most often Perlite (the other expanded lightweight aggregate), Mica (the parent mineral) and Exfoliated clays. A refractive index of 1.52-1.58 and a specific gravity near 2.4-2.7 unexpanded; 0.06-0.16 bulk density once exfoliated separate it quickly.
What is vermiculite used for besides jewellery?
heavy industry, architecture and interiors and filtration. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for vermiculite?
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 vermiculite