Abstract Electrodeposition of silicon from a cryolite based electrolyte at a relatively low temperature is a promising approach to generate high purity silicon. In order to obtain fundamental data pertaining to electrowinning of silicon from cryolite–SiO 2 melts, charge transport properties of the melt such as conductivity and electronic and ionic transference numbers were measured. Each property was determined for a range of temperatures and SiO 2 contents. It was found that addition of silica to cryolite generally decreases the transport rate of charge carriers. The temperature on the other hand had a positive effect on the electronic and ionic conductivities. The variations arise from the structural changes in the melt, particularly formation of complex ions involving Na, Si, and Al.