The present invention provides .alpha.-alumina powders comprising .alpha.-alumina particles of which at least 80% of the .alpha.-alumina particles have a particle size of less than 100 nm. The invention also provides slurries, particularly aqueous slurries, which comprise .alpha.-alumina powders of the invention. The invention further provides methods of manufacturing .alpha.-alumina powders and .alpha.-alumina slurries of the invention and methods of polishing using same.