Abstract: The present invention relates to an enrichment process, by flotation, of sedimentary ores containing phosphate, and comprising a gangue of the carbonated type and in some cases a gangue of the siliceous type, wherein an amphoteric product of formula ##STR1## is at least used as collecting agent, in which formula: R is of form R.sub.1 or R.sub.1 O--, R.sub.1 being a saturated or unsaturated alkyl radical, either linear or branched, and comprising between 5 and 19 carbon atoms.R' and R" are H or --Aq--Z, bearing in mind that for R", when n is greater than 1, there can be in the molecule simultaneously radicals H and radicals --Aq--Z.Ap and Aq are polymethylene chains containing between 1 and 4 carbon atoms,n is a number equal to O or an integer between 1 and 5,Z is a radical selected from the carboxylic, the sulphonic and the phosphonic radicals, and in obtaining the flotation of the carbonated gangue by a reverse flotation in "basic medium .