Abstract: The present invention relates to a polishing composition comprising water, alumina, and a chelating agent. It may optionally be incorporated with an aluminum salt and/or boehmite. The present composition permits efficient polishing and gives a polished surface having superior surface properties. The composition is suitable for polishing a memory hard disk.

Abstract: The present invention relates to a polishing composition comprising water, .alpha.-alumina and boehmite. The addition of boehmite contributes to an improvement of the polishing performance to provide an excellent polished surface and a high polishing rate. The polishing performance can further be improved by incorporating at least one member selected from the group consisting of a water-soluble metal salt, an ammonium salt and a metal nitrite. The polishing composition of the present invention is suitable for polishing metals, plastics or glass. It is particularly useful for polishing a surface of a memory hard disk plated with nickel or a nickel alloy.