Calcium carbonate is the most widely used mineral in the paper, plastics, paints and coatings industries both as a filler – and due to its special white color – as a coating pigment. In the paper industry it is valued worldwide for its high brightness and light scattering characteristics, and is used as an inexpensive filler to make bright opaque paper. Filler is used at the wet-end of paper making machines, and calcium carbonate filler allows for the paper to be bright and smooth. As an extender, calcium carbonate can represent as much as 30% by weight in paints. Calcium carbonate also is used widely as a filler in adhesives, and sealants. Calcium carbonate is a difficult type of slurry to pump because of the high percentage of very abrasive fine solids. Usually pumps have to be replaced on a consistent basis due to the abuse they receive while pumping this type of slurry.