In this paper, alpha-chloro-oleate acid (alpha-COA) and sodium hexametaphosphate (SHMP) were employed as collector and depressant in the flotation separation of magnesite from dolomite respectively. Properties of these two reagents were investigated through micro-flotation tests, zeta potential measurements, contact angle measurements and theoretical computation of adsorption energy based on conceptual density functional theory (DFT). Zeta potential measurements results revealed that SHMP was selectively adsorbed on the surface of dolomite, which leads to an exclusively depressing effect on dolomite. Results of contact angle measurements and theoretical computation indicated that alpha-COA had a stronger collecting ability to magnesite because of a stronger adsorption occurred on the surface of magnesite. In micro-flotation of artificially mixed minerals, separation of magnesite from dolomite with Gaudin's selectivity index up to 6.42 was succeeded using alpha-COA as collector and SHMP as depressant. (C) 2020 Elsevier B.V. All rights reserved.