The formation of slime particles in processes of minerals grinding limits froth flotation. Minera de Orgiva S.C. (Spain) produces slime sludge containing 41.05% of CaF2 from a fluorite ore. Slimes have a very small particle diameter with very high specific surface area making this material difficult to process by froth flotation even when the grade of the material is high. Furthermore, removing this fraction of the mineral from the flotation process generates a waste that causes the appearance of slagheap that affects negatively the environment. This work studies the influence of aeration flow rate, time of flotation, agitator speed and pH in the flotation process of fluorite slimes. Results were adjusted to a polynomial mathematical model. An optimum 76.21% of fluorite grade was achieved with a metallurgical recovery of 70.57% using values of 0.8 m(3)/h of air flow rate, 7 min of flotation time, 1100 rpm and pH of 9.25. (C) 2020 Elsevier B.V. All rights reserved.