An often asked question when coming to buy Aluminium Oxide, especially with them having large price differences.
They all come from the same raw material bauxite, however they have been through different processes to get them to the colour they are. Bauxite in its raw from contains other impurities, so it goes through different process to extract these impurities. The more processes it goes through the purer it is and the more expensive it is.
Pink is a harder aluminium oxide due to the addition of chrome in it, hence giving a pink colour, and being a premium price.
White has had the iron removed from the bauxite and is used in blasting processes which requires very little metal contamination, such as Rolls Royce air industry.
Brown is harder than white because it contains more iron, and is a more commonly used as it has a lower price point due to being through less processes to remove the contaminations.