A clay or claylike material with a high adsorptive capacity, consisting largely of the clay minerals montmorillonite and palygorskite. Used originally in England for whitening, degreasing, or fulling (shrinking and thickening by application of moisture) woolen fabrics; fuller's earth now is extensively used as an adsorbent in refining and decolorizing oils and fats; it is a natural bleaching agent. Its color ranges from light brown through yellow and white to light and dark green; it differs from ordinary clay by having a higher percentage of water and little or no plasticity, tending to break down into a muddy sediment in water. Fuller's earth probably forms as a residual deposit by decomposition of rock in place, as by devitrification of volcanic glass. The term is applied without reference to any particular chemical or mineral composition, texture, or origin.