Abrasive

Any hard, sharp material that wears away a softer, less resistant surface when the two are rubbed together. They are used to used to polish metals, stone, wood, glass, and other materials. They are sold as powders, slurries, and as abrasive cloths, papers, and wheels. They are characterized by hardness and particle size. Their hardness can be measured on the Mohs' scale in which the diamond is rated as a 10.