A process for preparing whitened fly ash includes the steps of: (a) subjecting fly ash to a size classification step to obtain size classified fly ash having a particle size such that at least 90 wt % has a particle size of from 44 μm to 250 μm; (b) optionally, contacting the size classified fly ash from step (a) with water to form a slurry, wherein the slurry has a solid content of less than 40 wt %; (c) subjecting the slurry obtained in step (b) to an exhaustive magnetic separation step to form magnetically treated fly ash, wherein the exhaustive magnetic separation step includes a first magnetic extraction step and a second magnetic extraction step, wherein the second magnetic extraction step is carried out at a higher magnetic field strength than the first magnetic extraction step; and (d) subjecting the magnetically treated fly ash obtained in step (c) to milling to form whitened fly ash.