Diatomite: Extraction
Why ancient lake beds make cheap open pits
What this tab covers How it is mined, drilled or grown, and processed into a tradeable form: the main methods compared, their unit economics, by-products, and the companies that do this work globally and in India.Diatomite is the accumulated silica cell walls of dead diatoms, deposited in ancient lakes and seas. It is also called kieselguhr, and an impure Danish form is moler. US deposits lie at or near the surface in California, Nevada, Oregon and Washington, so open pits are cheap. Elsewhere, underground mining is fairly common. Crude ore is dried, milled and classified. Filter grades are calcined, often with a flux, to fuse fines and tune pore size. Many forms contain crystalline silica, a health hazard in processing.
Diatomite is mined like a soft rock and processed mainly by heat and air. The main split is between filter-aid grades, which are calcined and carefully classified, and natural grades for fillers, absorbents and aggregates. Because most deposits in the US are at the surface, mining is cheap; the cost is in drying, calcining and dust control. Outside the US, underground mining is common. Danish moler is a separate product, an impure clay-rich diatomite used for absorbents and insulation.
Methods compared
| Method | Share of supply | Typical scale | Recovery / efficiency | By-products | Unit cost |
|---|---|---|---|---|---|
| Open-pit mining with calcined filter-aid production (US West) | US 720,000 t in 2025, about 29% of world output (USGS) | Nine US processing plants in 2025 (USGS); US average 80,000 t per plant | n/a | n/a | Not published; US average value $580/t f.o.b. plant in 2025, up from $410/t in 2021 (USGS) |
| Moler mining and processing (Denmark) | Denmark 380,000 t processed in 2025, about 15% of world output (USGS) | n/a | n/a | n/a | Not published |
| Open-pit and underground mining (France, Argentina, China, Turkey, Mexico, Peru) | France 250,000 t, Argentina 190,000 t, Turkey 150,000 t, China 140,000 t, Mexico 100,000 t and Peru 99,000 t in 2025 (USGS) | Imerys bought three French and Italian diatomite and perlite assets from Chemviron in January 2025, a business with about EUR 50 million of 2024 revenue | n/a | n/a | Not published |
How each method works
Open-pit mining with calcined filter-aid production (US West)Ore is mined from shallow pits, dried, milled and calcined, sometimes with a soda ash flux, then air-classified into grades by permeability for brewing, wine, water and chemical filtration.
Cheap surface ore and high-value filter grades; crystalline silica in calcined grades needs strict exposure control.
USGS MCS 2026 Moler mining and processing (Denmark)Clay-rich diatomite on the Limfjord islands is mined in pits and processed into absorbents, cat litter, insulating bricks and fillers rather than premium filter aids.
Large volume of mid-value products; less suited to fine filtration.
USGS MCS 2026 Open-pit and underground mining (France, Argentina, China, Turkey, Mexico, Peru)Smaller deposits are mined in pits or underground where topography requires, and processed into filter aids and fillers mainly for regional markets.
Serves nearby markets; transport cost limits reach.
USGS MCS 2026; Imerys release (Jan 2025) Unit economics are indicative ranges from the sources named; costs vary widely by deposit, region and year.Who does it: global
| Company | Country | Activity | Volume | Year | Source |
|---|---|---|---|---|---|
| Imerys Volume not published; acquired business had about EUR 50 million revenue and 130 staff in 2024 | France | diatomite filter aids and fillers (US, Europe); acquired Chemviron's European diatomite and perlite business in January 2025 | not published | 2025 | Imerys press release (Jan 2025) |
| EP Minerals (U.S. Silica) Volume not published | US | diatomite mining and processing in Nevada and Oregon | not published | 2025 | Company information; parent privately held |
| Dicalite Management Group Volume not published | US | diatomite and perlite filter aids | not published | 2025 | Company information |
| Damolin Volume not published | Denmark | moler (diatomite) absorbents and insulation | not published | 2025 | Company information |
| Showa Chemical Industry Volume not published | Japan | diatomite filter aids | not published | 2025 | Company information |
Who does it: India
India is not listed among diatomite producers by USGS (2025) and is not among the top six importers by value (UN Comtrade 2024). No Indian producer with published volumes was found.