suitable amines include higher alkyl amines such as dodecylamine pentadecylamine and octadecylamine primary amines including mixed amines such as for example coconut oil amines beef tallow amines and soybean oil amines secondary amines such as n dodecylpropylenediamine n pentadecylethylenediamine n decylhexamethylenediamine and beef tallow propylenediamine and tertiary amines such as condensates of stearic acid with n oleyl n diethylethylenediamine or triethanolamine and n acylates of alkylenetriamines with inorganic acids such as hydrochloric acid and phosphoric acid or with organic acids such as acetic acid propionic acid tertaric acid and succinic acid a particularly preferred amine is sold under the trade name az 36a amine by az products company lakeland fl the cationic collector component is generally added to the pulp in an amount of about 0 05 to 0 5 lbs of amine per metric ton of ore preferably from about 0 1 to 0 3 lbs ton and most preferably from about 0 15 to 0 25 lbs ton the weight ratio of the anionic collector to the cationic collector in the mixed collecting agents of the present invention is within the range of about 2 to 10 and preferably within the range of about 4 to 6 it is necessary in practicing the present invention to add a flotation activator to the pulp which specifically activates the flotation of quartz or silica examples of suitable silica activating ions include calcium magnesium aluminum and iron but other ions known to be effective in activating the flotation of silica with an anionic collector also can be used calcium is an especially preferred silica activating ion since it is normally present in sufficient quantities i e about 10 30 ppm in municipal water which is typically used to.