Pure colemanite and realgar crystals, collected from Emet Colemanite deposit in Kutahya, Turkey, were used to determine the adsorption mechanisms of flotation reagents on mineral surfaces. The floatability of pure minerals and separation conditions by flotation were also investigated. Infrared spectrophotometer studies revealed that sodium oleate was adsorbed chemically on colemanite surfaces, and floated pure colemanite minerals with over 98% recovery. Potassium amyl xanthate was determined to be the best collector for realgar, and floated pure realgar minerals with over 88% recovery. The optimum separation conditions were also determined by means of flotation by using artificial mineral mixtures. The separation was obtained by floating realgar with potassium amyl xanthate, and colemanite was left in the suspension. Finally, optimum conditions were applied to a natural sample. Realgar was floated off and a colemanite concentrate was obtained in the suspension having 96.99% B2O3 recovery and 33.93% B2O3 grade with 860 ppm As content. (C) 2003 Elsevier Science Ltd. All rights reserved.