In this study, effects of concentration of anionic collectors like KO1, Flotinor FS-2 and modifying reagents like MgCl2, CaCl2, Na2SiO3&BULL; 5H(2)O and CMC on surface properties of huntite and hydromagnesite as unusual carbonates have been investigated. The results of microflotation tests have indicated that KO1 is more efficient than Flotinor FS-2. And also, MgCl2, CaCl2 have a negative effect on the flotability of huntite and hydromagnesite. Na2SiO3&BULL; 5H(2)O has no significant effect on the flotability of these unusual carbonates. On the other hand, CMC has acted as a depressant on huntite but there is no clear effect on hydromagnesite. © 2004 Elsevier Ltd. All rights reserved.