Diatomite is a soft, chalky sedimentary rock made almost entirely of the fossilized remains of diatoms, single-celled algae that lived in ancient lakes and oceans. Its silica content can exceed 91 percent, and its structure is riddled with microscopic pores, giving it an unusually low density and a remarkably high surface area for a natural material. Those properties make diatomite one of the most versatile industrial minerals on Earth, with uses ranging from filtering beer to cleaning up oil spills, killing insects without chemical pesticides, and even powering experimental lithium-ion batteries.
How Diatomite Forms
Diatoms are microscopic algae that build intricate glass-like shells out of silica dissolved in the water around them. When they die, their shells settle on the bottom of lakes or ocean floors. Over thousands to millions of years, these layers of shells compact into a lightweight, porous rock. The result is diatomite, sometimes called diatomaceous earth (DE) when sold in powdered form.
Not all diatomite is the same. Marine deposits, formed in oceans, tend to be higher quality and more extensive than lacustrine deposits, which formed in freshwater lakes. Marine environments offer more stable conditions of temperature, salinity, and nutrients, which produces more uniform diatom shells. Despite this, most of the world’s known diatomite deposits are actually lacustrine in origin. The highest-quality material, predominantly from marine sources, ends up in filtration products, while both types are used for fillers, absorbents, and abrasives.1U.S. Geological Survey. Chapter D: With or Without Salt-a Comparison of Marine and Continental-Lacustrine Diatomite Deposits
Major deposits are found in the western United States (particularly California and Nevada), parts of Europe, China, and several countries in Africa and South America. The United States has historically been the largest producer, with the Lompoc deposit in California being one of the most significant sources worldwide.
What Makes Diatomite Special
The physical properties of diatomite are unusual for a rock. Studies of raw diatomite samples show a total porosity of around 70 to 72 percent, meaning the rock is more empty space than solid material. Its density sits at roughly 2 g/cm³, and it is soft enough to crumble between your fingers. The chemical composition is dominated by amorphous (non-crystalline) silica, with minor amounts of quartz, muscovite, and other minerals. That amorphous silica structure remains thermally stable up to about 1,050°C before it begins to crystallize.2Geologica Macedonica. Diatomite – evaluation of physico-mechanical, chemical, mineralogical and thermal properties
The pores in diatomite exist at the nanometer scale, inherited directly from the intricate architecture of diatom shells. Under an electron microscope, you can see the original patterns: tiny round holes arranged in regular grids, elaborate radial structures, and channels running through the silica walls. This natural nanostructure is what gives diatomite its enormous surface area relative to its weight, and it is the reason the material excels at absorbing liquids, trapping particles, and interacting with chemicals at the molecular level.
Filtration, the Biggest Industrial Use
If you have ever drunk a clear beer, there is a good chance diatomite played a role. Filtration is the single largest use of diatomaceous earth worldwide, and the brewing industry is one of its biggest customers. The idea is straightforward: a slurry of diatomite powder is coated onto a filter screen, forming a porous “cake.” When beer, wine, juice, or water is pushed through that cake, the microscopic pores trap yeast cells, bacteria, and other particles while letting the liquid pass through clear.
Research has shown that calcining diatomite (heating it to around 1,000°C) improves its filtration performance by altering particle size and pore structure. In tests using beer from a commercial Turkish brewery, calcined diatomite achieved high flow rates and good filtrate clarity comparable to commercial filter aids.3Elsevier (International Journal of Mineral Processing). Improvement in filtration characteristics of diatomite by calcination The same principle applies to swimming pool filters, water treatment plants, and pharmaceutical manufacturing, anywhere you need to remove fine particles from a liquid without adding chemicals.
Diatomite’s porous structure also makes it useful as a support for catalysts. In industrial chemistry, the material serves as a carrier for sulfuric acid catalysts because its pores provide ideal reaction spaces for synthesizing sulfur trioxide, a key step in producing sulfuric acid.4Applied Surface Science. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment
How Diatomite Kills Insects Without Chemicals
One of diatomite’s most popular consumer uses is as a pesticide, and the mechanism is entirely mechanical, not chemical. When insects walk through diatomaceous earth powder, the tiny silica particles stick to their exoskeletons and begin absorbing the waxy lipid layer that normally keeps moisture sealed inside their bodies. Without that waterproof coating, the insect dehydrates and dies.
Researchers have confirmed this mechanism using respirometry and electron microscopy. Studies on insects treated with diatomaceous earth found that both cuticular and respiratory water loss increased after exposure. Scanning electron microscopy showed the lipid-absorbing properties of diatomite particles on the cuticle surface.5PubMed. Diatomaceous earth as insecticide: physiological and morphological evidence of its underlying mechanism Work on cockroaches using nano-sized diatomaceous earth particles went further, showing that the smaller particles could actually penetrate into the cuticular matrix itself, disrupting lipid-rich layers and damaging epidermal cells from the inside rather than just the surface.6Physiological Entomology. Comparative efficacy of natural and nano‐sized diatomaceous earth against American cockroach, Periplaneta americana, for sustainable control
This matters because diatomaceous earth is one of the few pest control options that insects cannot develop chemical resistance to. The kill mechanism is physical, not biochemical, so there is no metabolic pathway for the insect to evolve around. That makes it attractive for stored grain protection, household pest control, and organic agriculture. The main practical limitation is that it works slowly (often taking days rather than hours) and loses effectiveness when wet, since moisture clogs the pores that do the absorbing.
Cleaning Up Oil Spills and Chemical Contamination
The same absorbent properties that make diatomite deadly to insects make it useful for soaking up hazardous liquids. Industrial-grade diatomite is widely used to clean up oil spills, solvent leaks, and chemical accidents in factories and warehouses. You may have seen the grayish granules scattered on garage floors or gas station forecourts to soak up dripped fuel.
Research on Polish diatomite found that it could absorb oil derivatives at about 130 percent of its own weight, a result the researchers described as commercially significant because it outperformed competing absorbent materials.7Journal of Cleaner Production. Use of diatomite from Polish fields in sustainable development as a sorbent for petroleum substances Other work has shown that treating diatomite with acid and heat can boost its oil-absorbing capacity even further. Acid-activated diatomite heated to 400°C demonstrated the highest sorption capacity for crude oil in comparative tests.8Eurasian Chemico-Technological Journal. Modification of Diatomite Mineral Sorbent for the Cleanup of Petroleum Spills on Water Surfaces
Beyond oil, diatomite is being studied as a tool for removing heavy metals and industrial dyes from wastewater. Modified diatomite has achieved a lead removal efficiency of about 90 percent from aqueous solutions under optimized conditions.9Journal of Hazardous Materials Advances. Adsorptive removal of lead ions from wastewater using modified diatomite Similar results have been reported for copper, zinc, and several industrial dyes, with removal efficiencies above 80 percent at room temperature and normal pH levels.10Processes. Dyes and Heavy Metals Removal from Aqueous Solutions Using Raw and Modified Diatomite Calcined diatomite has also shown strong capacity for adsorbing radioactive thorium from solution.11ScienceDirect (Elsevier / Applied Clay Science). Adsorptive removal of thorium (IV) using calcined and flux calcined diatomite from Turkey: Evaluation of equilibrium, kinetic and thermodynamic data These environmental cleanup applications are still largely in the research stage, but the low cost and natural abundance of diatomite make it a compelling alternative to synthetic adsorbents.
Lightweight Construction Materials
Diatomite’s low density has caught the attention of building materials researchers. Because the rock is mostly air by volume, bricks and blocks made from it weigh far less than conventional clay bricks, which matters for insulation, structural load, and transport costs.
Laboratory work has produced lightweight bricks from diatomaceous earth mixed with lime and gypsum. Bricks made with untreated diatomite, 15 percent lime, and 5 percent gypsum achieved a compressive strength of 14.5 MPa at a density of just 0.88 g/cm³, roughly one-third the density of a standard clay brick. Using diatomite that had been calcined at 500°C pushed the strength up to 17.5 MPa while dropping the density even further to 0.73 g/cm³.12Ceramics International. Lightweight bricks made of diatomaceous earth, lime and gypsum The diatomite contributes what is known as pozzolanic activity, meaning it reacts with lime in the presence of water to form compounds that act like cement, binding the brick together without needing to be fired at high temperatures.
Diatomite also shows up in thermal insulation products and as an additive to concrete and plaster, where its porosity helps reduce weight and improve insulating properties. In parts of the world where diatomite is locally abundant, it has a long history as a construction material, with some traditional buildings in Turkey, Greece, and parts of Africa incorporating diatomite blocks or plaster.
The Health Question: Is Diatomite Safe?
For consumers using food-grade diatomaceous earth around the home or garden, the health risks are minimal. The material is approved as a food additive and as an anti-caking agent in animal feed. The amorphous silica in unprocessed diatomite is generally considered a nuisance dust, not a serious health hazard when exposure is occasional and limited.
The picture changes dramatically for workers in diatomite mines and processing plants. When diatomite is heated during calcination, some of its amorphous silica converts to crystalline forms, particularly cristobalite, which is a recognized human carcinogen when inhaled over long periods. A major study of over 2,300 white male workers in California’s diatomaceous earth industry found a significant relationship between cumulative exposure to respirable crystalline silica dust and lung cancer mortality. Workers with average cumulative exposure faced roughly 1.6 times the lung cancer death rate compared to unexposed individuals. The researchers estimated that 45 years of occupational exposure at the existing workplace standard would result in about 19 excess lung cancer deaths per 1,000 workers, and they concluded that the occupational health standards of the time may not have been adequately protective.13Occupational and Environmental Medicine. Crystalline silica exposure and lung cancer mortality in diatomaceous earth industry workers: a quantitative risk assessment
The practical takeaway: the danger comes from inhaling fine crystalline silica dust, especially cristobalite, over months and years of occupational exposure. If you are using food-grade diatomaceous earth in your garden, wearing a basic dust mask during application is a reasonable precaution. If you are working in a processing facility where calcined diatomite dust is airborne, the risks are real and regulated, and proper respiratory protection is not optional.
Drug Delivery and Biomedical Research
The intricate nanoporous structure of diatom shells has attracted researchers working on drug delivery systems. The idea is to load medication into the pores of cleaned, purified diatom frustules (the silica shells) and use them as microscopic capsules that release the drug slowly over time. This would be cheaper than manufacturing synthetic silica nanoparticles from scratch, since nature has already built the container.
Early studies demonstrated that diatom microcapsules could achieve drug-loading capacities of 14 to 22 percent by weight and sustained drug release over two weeks.14PubMed. Silica microcapsules from diatoms as new carrier for delivery of therapeutics Further work showed that by chemically modifying the surface of diatomite microparticles, researchers could tune how much drug the particles absorbed and how quickly they released it, for both water-loving and water-repelling drugs.15PubMed. Tuning drug loading and release properties of diatom silica microparticles by surface modifications Diatomite-derived biosilica has been highlighted as a particularly promising candidate for drug delivery because of its biocompatibility, high surface area, low cost, and the ease with which its surface can be chemically modified.16PubMed. Nature engineered diatom biosilica as drug delivery systems
This remains a research frontier rather than something you would find in a pharmacy today. But the appeal is clear: diatoms are abundant, renewable (they grow in water), and their shells are already the right size and porosity for interacting with biological systems. Most synthetic nanoparticles require expensive, energy-intensive fabrication processes that diatomite could potentially bypass.
Biosensors and Optical Applications
Diatom shells do something unexpected when they interact with light. Their regular, repeating nanostructures can act like tiny optical gratings, diffusing and modifying light in ways that researchers have begun to exploit for sensing applications. When certain molecules bind to the surface of a diatom frustule, the way the shell emits or scatters light changes in a measurable way.
Researchers have chemically modified diatom frustules to bind antibodies, then measured changes in the shells’ photoluminescence when those antibodies encountered their target molecules. The system achieved a detection limit of 100 nanomolar and sensitivity comparable to standard laboratory biosensor equipment, demonstrating potential for what some researchers call “lab-on-a-particle” technology.17PubMed. Marine diatoms as optical biosensors The idea is that cheap, naturally produced silica structures could replace expensive synthetic components in diagnostic devices, particularly for point-of-care testing in low-resource settings.
Next-Generation Battery Anodes
One of the more surprising applications under development involves using diatomite as a raw material for lithium-ion battery anodes. Silicon is an extremely promising anode material because it can store far more lithium than the graphite used in today’s batteries. The problem is that producing pure silicon is energy-intensive and expensive. Diatomite offers a shortcut: its silica can be converted to nanosilicon through a chemical process called magnesiothermic reduction, which uses magnesium at much lower temperatures than the traditional industrial method.
Researchers have demonstrated that nanosilicon derived from diatomite can serve as a high-rate-capable battery anode, maintaining good performance even when charged and discharged rapidly.18Scientific Reports. Carbon-Coated, Diatomite-Derived Nanosilicon as a High Rate Capable Li-ion Battery Anode Other groups have developed methods to create hierarchically porous silicon particles from diatomite, where the original diatom shell structure acts as both a silicon source and a structural template, producing composites with crystalline silicon domains just 10 to 30 nanometers in size embedded in a supportive matrix.19Advanced Functional Materials. Diatomite‐Derived Hierarchical Porous Crystalline‐Amorphous Network for High‐Performance and Sustainable Si Anodes
The porosity that nature built into diatom shells turns out to be an advantage here, too. Silicon anodes swell dramatically when they absorb lithium during charging, and that swelling causes cracking and rapid degradation. The built-in pore network in diatomite-derived silicon gives the material room to expand without breaking apart, potentially solving one of the biggest obstacles to silicon-based battery technology. Whether this approach can scale to commercial manufacturing remains an open question, but the combination of cheap raw material, low processing temperature, and a naturally engineered nanostructure has generated genuine enthusiasm in materials science circles.
Everyday Products You Might Not Expect
Beyond the industrial and high-tech applications, diatomite turns up in a surprising number of everyday consumer products. Toothpaste is one: the fine, mildly abrasive particles in many whitening toothpastes are diatomaceous earth. The material is soft enough not to scratch tooth enamel but hard enough to scrub away surface stains. Similar logic applies to metal polishes, facial scrubs, and some household cleaning powders.
Cat litter is another familiar product that sometimes contains diatomite, valued for its absorbency and odor-controlling properties. In agriculture, food-grade diatomaceous earth is mixed into stored grain to protect against weevils and other pests without leaving chemical residues. Some gardeners dust it around plants to deter slugs and crawling insects, though its effectiveness drops sharply once it gets wet. Pool-grade diatomaceous earth, which has been calcined and contains more crystalline silica, is sold for swimming pool filtration systems but should never be used interchangeably with food-grade material because of the higher crystalline silica content.
The distinction between food-grade and calcined (pool-grade or industrial-grade) diatomaceous earth is one that consumers regularly get wrong, and it matters. Food-grade DE is mostly amorphous silica and is safe for incidental ingestion and household use. Calcined DE has been heated to the point where significant crystalline silica has formed, making it effective for filtration but genuinely hazardous to inhale. If you are buying diatomaceous earth for pest control or garden use, make sure the label specifies food-grade. If it is sold for pool filters, keep it away from people and pets.