This paper is reporting the data of a preliminary study on heavy metals distribution in the fluid and solid phases involved in dry and classified aluminum hydroxide production through the Bayer process. For heavy metals released in the fluid phases, the main source of contamination is the bauxite through its mineralogical phases soluble or insoluble in alkaline solution. It was shown that the predominant way to transfer contaminating elements in aluminum hydroxide particles is the occlusion of very fine particles coming from mineralogical phases of bauxite residue. Newborn mineralogical phases from bauxite residue, like poor crystallized sodalite and cancrinite, are the most active occlusion contaminants.