In this paper, the particle interaction between the fine fluorite and quartz (all less than 10 mu m) and its effect on the fluorite flotation were studied mainly by rheological measurements, optical observation and micro-flotation tests. Sodium oleate was used as the fluorite collector. The yield stress, which is a rheology parameter, was utilized to quantify the aggregation degree of the particles and evaluate the strength of the net-work structures in flotation slurry. The yield stress value of fine fluorite slurry as a function of the solid concentration, pH, percentage of the fine quartz and collector concentration was measured. The rheological measurements and the optical observation results show that the fluorite particles could partially aggregate into flocs in the pH range of 5-10 and form net-work structure in suspensions, while quartz particles could not aggregate across the whole pH range tested. When quartz and fluorite particles were mixed in water, the yield stress of the mixed mineral slurry was much higher than that of the single mineral slurry, demonstrating a strong hetero-coagulation between the two minerals. The flotation performance of the fine fluorite particles with different degree of hetero-coagulation (caused by the different percentage of fine quartz) was tested. The hetero-coagulation exhibited a detrimental effect on the fluorite flotation, manifesting as decreased flotation recovery and decreased flotation rate. It was found that the hetero-coagulation deteriorated the fine fluorite flotation by forming strong network structures that could interfere with the rising processes of the bubbles carrying valuable mineral particles. The research provides a new way for quantifying the particle interactions and may potentially be used for regulating the flotation operations in the fluorite flotation plants. (C) 2019 Elsevier B.V. All rights reserved.