Abstract: Abrasive grains according to the present invention are abrasive grains in which the surfaces thereof are coated with an additive and that are formed of inorganic abrasive particles having a positive zeta potential at pH 8 or lower. Also, it is preferable that the additive be picolinic acid or glutamic acid. It is preferable that the inorganic abrasive particles be cerium oxide particles. The present invention provides abrasive grains in which the surfaces thereof are coated with picolinic acid or glutamic acid and that are formed of cerium oxide particles having a positive zeta potential at pH 8 or lower, wherein the abrasive grains are manufactured by means of an abrasive grain manufacturing method including a step for performing wet grinding of cerium oxide in the presence of picolinic acid or glutamic acid.

Abstract: Disclosed is a polishing slurry for sapphire polishing that is capable of obtaining polishing speeds and smooth surfaces during the polishing of sapphire substrates that are equivalent to or better than in prior polishing processes even if the number of polishers and polishing hours are reduced. Also disclosed is a sapphire substrate polishing method. The slurry includes alumina abrasives and has a pH adjusted to the range of 10.0 to 14.0, and the sapphire is polished by means of the CMP technique by applying said slurry. The aforementioned alumina abrasives more preferably include at least ?-alumina, and the content thereof is more preferably 0.01 to 50 wt %. The mean particle size of the aforementioned alumina abrasives is preferably 0.05 to 10 ?m.