It is a naturally occurring white or brown clay containing aluminum magnesium silicate. Fuller’s earth acts as a catalyst and was named for a process known as fulling—a process used to clean grease from wool and cloth. It is currently used for lightening the color of oils and fats, as a pigment extender, as a filter, as an absorbent (for example, in litter boxes to absorb animal waste), and in floor sweeping compounds.