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Diatomaceous earth (also known as diatomite, DE or kieselguhr) is a naturally occurring, light-colored, solid material that is easily crumbled into a fine dust. It consists primarily of the fossilized remains of diatoms (a type of hard-shelled algae). Its typical chemical composition is 86% silicon, 5% sodium, 3% magnesium, and 2% iron.
Commercial applications
The high absorbency and porosity and low density of diatomaceous earth make it an appealing material to use in a number of commercial applications.
- In 1867, Alfred Nobel discovered that nitroglycerin could be made much more stable by mixing it with diatomaceous earth. He patented this mixture as dynamite.
- Probably the most common use of diatomaceous earth is a filter medium. It is commonly used to filter water and other fluids such as beer.
- It is used as an insecticide. The material causes small cuts in the waxy outer layer of insects, causing them to dehydrate. It is sometimes mixed with an attractant or other additives to increase its effectiveness.
- Its absorbent qualities make it useful for spill cleanup and the U.S. Center for Disease Control recommends it to clean up toxic liquid spills.
- More recently, diatomaceous earth has been employed as a primary ingredient in a type of cat litter. The type of silica used in cat litter comes from freshwater sources and does not pose a significant health risk to pets or humans.
Geology
Because diatomaceous earth forms from the remains of water-borne diatoms, it is found in proximity to either current or former bodies of water. Diatomaceous earth is generally divided into two categories based upon source: freshwater and saltwater. Freshwater diatomaceous earth is mined from dry lakebeds and is characteristically low in crystalline silica content. Saltwater diatomaceous earth, in contrast, contains a high crystalline silica content making it a useful material for filters due to the sieve-like features of the crystals.
Specific varieties
- Tripolite refers to the variety found in Tripoli, Libya.
- Bann clay refers to the variety found in the Lower Bann valley in Ireland.
Safety Considerations
The absorbent qualities of diatomaceous earth can result in a significant drying of the hands if handled without gloves. The saltwater form contains the highly crystalline form of silica resulting in sharp edges. The sharpness of this version of the material makes it dangerous to breathe and a dust mask is recommended when working with it.
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