Kiselgur

Kiselgur, known in English as diatomaceous earth (DE) or kieselguhr, is a porous sedimentary rock formed from the fossilized remains of diatoms, a group of hard-shelled algae. It is rich in silica and typically appears as a soft, friable material that can be ground into a fine white to tan powder. The diatom frustules, or silica shells, accumulate in aquatic environments (marine and freshwater) and over time form diatomite deposits that are mined and processed for various uses.

Composition and properties: DE is largely composed of amorphous silica with varying amounts of impurities. It has high porosity and a large surface area, giving it strong filtration and absorptive qualities as well as mild abrasive properties. DE is sold in different grades, including food-grade and filter-grade (the latter is highly purified for filtration applications). Some forms may contain crystalline silica, which poses health risks if inhaled; care should be taken to minimize exposure.

Uses: The primary industrial use of diatomaceous earth is as a filtration aid for liquids such as beer, wine, juices, and drinking water. It is also employed as a mild abrasive in polishes and toothpaste, and as a filler in paints, plastics, and cosmetics. In pest control, diatomaceous earth is used as a mechanical insecticide: its fine dust damages the protective outer layer of insects, leading to desiccation. It can also serve as a carrier for pesticides or nutrients.

Safety and handling: Inhalation of respirable silica dust can cause lung disease, including silicosis. Food-grade and cosmetic-grade DE are subject to quality controls to limit crystalline silica content. Proper ventilation, dust suppression, and personal protective equipment are advised when handling non-food grades.