To obtain a sound base for further development of a refining process in which Si is precipitated from aluminium melts; a series of experiments have been performed in a Bridgman furnace. Compositions studied are in the range 17-38% Si, and experiments have been done with the hot zone up and the hot zone down to study the effects of flotation and sedimentation as well as different convection conditions on silicon precipitation. The similarity in density between liquid aluminium and silicon crystals implies that the melt convection is important not only for the possible separation of the crystals in a gravity field, but also for the crystal morphologies, which have to be controlled to avoid inclusions of aluminium. At lower silicon contents the morphologies have a fish-bone or star-like shape, but as the Si content increases the morphology changes to plates, which becomes coarser with increase in Si concentrations. The growth pattern for coarse plates growing in the (1 1 1) planes tend to form pockets of aluminium, which will end up as inclusions during dissolution of the matrix.