Siderite-bearing hematite is a type of refractory iron ore, where fine particle aggregation or dispersion behavior is of importance for the separation efficiency. Hence, the aggregation characteristics of fine particles (hematite and siderite) using sodiumoleate (NaOl) as a flocculant were investigated through FBRM particle size analysis (a real-time particle characterization tool), zeta potential analysis, adsorption tests, contact angle measurements, and X-LVO theoretical calculations. The results showed that NaOl could interact with hematite and siderite when the pH value ranged from 5.0 to 9.0, in which the hydrophobic interaction played a leading role in inducing homo-aggregation and hetero-aggregation in the mineral particles. However, in the strong alkaline solution environment (pH = 11.0), NaOl could only interact with siderite and scarcely adsorbed onto the hematite surface, which was mainly covered with ferric hydroxyl compound (Fe-OH). This largely prevented the formation of hematite-hematite and hematite-siderite aggregates in the suspension. (C) 2020 Elsevier B.V. All rights reserved.