The facts
What tripoli actually is
Tripoli is classified as a friable, extremely fine-grained microcrystalline silica formed by the leaching of carbonate out of siliceous limestone, leaving a porous silica residue, with the composition SiO2, 98-99%, as microcrystalline quartz with particle size around 1-10 micrometres. It crystallises in the aggregate (cryptocrystalline trigonal quartz) system.
Colour comes from white, cream, pink and red from trace iron; colour grading is used commercially for buffing compounds, which is also what a laboratory looks at when it is asked whether a colour is natural.
Refractive index 1.54. Specific gravity around 2.55-2.65 true; low bulk density. Cleavage: none. Those three numbers separate it from most of what imitates it.
Where tripoli comes from
Tripoli is produced at Seneca and Newton County, Missouri, USA - the principal US source, Ottawa County, Oklahoma, USA, Alabama and Illinois, USA and Tripoli, Libya (the original namesake, largely historic).
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 tripoli is treated
Dried, milled, air-floated and graded by particle size; nothing chemical. Uses: buffing and polishing compounds for metal (the classic use, in bar form), toothpaste and dental polishing abrasives, paint and plastic fillers, foundry facings, and as a very mild abrasive where a harder grit would scratch. The name is used loosely - much material sold as tripoli is diatomite, and 'rottenstone' is a related but distinct decomposed siliceous limestone used in furniture finishing. HEALTH: it is crystalline silica in respirable particle sizes, so it is a silicosis hazard despite the soft feel, and this is often underestimated because the material seems so benign.
Treatment changes value, sometimes by a multiple, so it belongs in the description before the price and not after the sale.
What tripoli is confused with
In the trade tripoli is most often mistaken for, or substituted by, Diatomite (amorphous, often sold under the same name), Rottenstone, Pumice and whiting as polishing agents or Precipitated silica.
The separation is rarely a matter of opinion: refractive index 1.54 and specific gravity 2.55-2.65 true; low bulk density settle most of it in a minute, and magnification settles the rest.
What tripoli is used for
Demand for tripoli comes from abrasives, heavy industry and cosmetics, 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.
Durability and care
Hardness Individual particles 7, but the rock crumbles to powder between the fingers; cleavage none. 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 tripoli costs
As a guide, tripoli trades around $200-450 per tonne depending on grade and colour.
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 tripoli treated, and how?
Dried, milled, air-floated and graded by particle size; nothing chemical. Uses: buffing and polishing compounds for metal (the classic use, in bar form), toothpaste and dental polishing abrasives, paint and plastic fillers, foundry facings, and as a very mild abrasive where a harder grit would scratch. The name is used loosely - much material sold as tripoli is diatomite, and 'rottenstone' is a related but distinct decomposed siliceous limestone used in furniture finishing. HEALTH: it is crystalline silica in respirable particle sizes, so it is a silicosis hazard despite the soft feel, and this is often underestimated because the material seems so benign.
Where does tripoli come from?
Seneca and Newton County, Missouri, USA - the principal US source, Ottawa County, Oklahoma, USA, Alabama and Illinois, USA and Tripoli, Libya (the original namesake, largely historic). Origin affects price, so we name the locality rather than the country on every quote.
Is tripoli hard enough to wear every day?
Not really. At Individual particles 7, but the rock crumbles to powder between the fingers 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 tripoli cost?
Indicatively $200-450 per tonne depending on grade and colour. 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 tripoli confused with?
Most often Diatomite (amorphous, often sold under the same name), Rottenstone, Pumice and whiting as polishing agents and Precipitated silica. A refractive index of 1.54 and a specific gravity near 2.55-2.65 true; low bulk density separate it quickly.
What is tripoli used for besides jewellery?
abrasives, heavy industry and cosmetics. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for tripoli?
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 tripoli