The flotation response of collophane and dolomite using B-naphthyl sulfonate formaldehyde condensate (NSFC) as depressant has been investigated through micro-flotation and batch flotation in this paper. Their adsorption mechanisms were studied by means of zeta potential, contact angle, adsorption measurements and thermodynamics calculation. The flotation results indicated that NSFC exhibited a straining influence on the depression of dolomite and had little effect on the flotation of collophane minerals. Compared with the results achieved without the NSFC, the NSFA increased the collophane/dolomite selectivity index significantly. The zeta potential results showed a change in the zeta potential measurements of the minerals after NSFC interaction. This change was more significant in the zeta potential curves of dolomite than that of collophane. This difference is also verified by the results of the contact angle and adsorption measurements. The results of thermodynamics calculation indicated that the adsorption of NSFC at collophane and dolomite was chemisorption and physisorption, respectively. This study provides new insights into the separation of collophane minerals. (C) 2016 Elsevier B.V. All rights reserved.