The present invention relates to a froth flotation process in which silicates are separated from an iron ore in the presence of a collector containing a quaternary ammonium compound having the formula R.sub.1R.sub.1N.sup.+R.sub.3R.sub.4 1/z X.sup.z- (I), in which the groups R.sub.1 independently are hydrocarbon groups, preferably aliphatic groups containing 6-14 carbon atoms and/or the group R.sub.2--(OR.sub.7).sub.m--OR.sub.8--, where the groups R.sub.2 independently are acyl groups containing 6-14 carbon atoms, the groups R.sub.7 independently are alkylene groups containing 2-4 carbon atoms, the groups R.sub.8 independently are alkylene groups containing 2-3 carbon atoms and m is a number from 0-5, R.sub.3 and R.sub.4 independently are alkyl groups containing 1-4 carbon atoms or groups (R.sub.5O).sub.pH, where the groups R.sub.5 independently are alkylene groups having 2-4 carbon atoms and p is a number from 1-4, X is an anionic group, and z is the charge of the anion X. This collector has a high selectivity to concentrate silicates in the froth product, while a high yield of iron minerals is maintained in the bottom concentrate or concentrates.