Abstract: This application discloses a method of wet grinding crude phosphate rock containing clay minerals and the like impurities. The procedures of the invention produce a rock slurry of enhanced fluidity and a desired degree of economy; and the principles of the invention may be applied to rock slurries after size-reduction. The method of the invention contemplates introducing coarsely sized, crude phosphate rock with component clay minerals or the like into a grinding mill together with a suitable quantity of water and with an amount of a calcium-free alkaline amendment or additive material which is adequate to establish and maintain a pH of at least about 8.5 in the mixture.