Fuller's earth is any non-plastic clay or claylike earthy material used to decolorize, filter, and purify animal, mineral, and vegetable oils and greases.
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In 2005, the United States was the largest producer of fuller's earth with an almost 70% world share followed at a distance by Japan and Mexico.
Fuller's earth usually has a high magnesium oxide content. In the United States, two varieties of fuller's earth are mined, mainly in the southeastern states. These comprise the minerals montmorillonite or palygorskite (attapulgite) or a mixture of the two; some of the other minerals that may be present in fuller's earth deposits are calcite, dolomite, and quartz.
In England, fuller's earth occurs mainly in the Lower Greensand. It has also been mined in the Vale of White Horse, Oxfordshire, England. The Combe Hay Mine was a fuller's earth mine operating to the south of Bath, Somerset until 1979.[1] Other sites south of Bath included Frome, Lonsdale, Englishcombe Tucking Mill and Duncorn Hill.[2] Although these sites had been used since Roman times William Smith developed new methods for the identification of deposits of Fuller's earth to the south of Bath.[3] Other English sources include a mine near Redhill, Surrey (worked until 2000), and Woburn, Bedfordshire, where production ceased in 2004.
In some countries calcium bentonite is known as fuller's earth, a term that can also refer to attapulgite, a mineralogically distinct clay mineral that exhibits similar properties.
Hills, cliffs, and slopes that contain fuller's earth can be unstable, since this material can be thixotropic, when saturated by heavy rainfall.
The name reflects the first use of the material. In past centuries, fullers kneaded fuller's earth and water into woollen cloth to absorb lanolin, oils, and other greasy impurities as part of the cloth finishing process. Similarly, it has been used as an ingredient in powdered, "dry" shampoos. Fuller's earth was also sold in pharmacies until recently for compressing pills and cleaning hats and fabrics.[4]
Important uses are in absorbents and filters. Because of this, it is used (with activated charcoal) in the treatment of paraquat overdose to prevent the progression to pulmonary fibrosis. Fuller's earth is also used by military and civil emergency service personnel to decontaminate the clothing and equipment of soldiers and CBRN (Chemical Biological Radiological Nuclear) responders who have been contaminated with chemical agents.[5]
Fuller's earth was a key ingredient in the special effects process developed to simulate the tornado in the 1939 film, The Wizard of Oz.