Abstract: Novel organosilicon-treated cosmetic powders, for example, a pigment, extender pigment or filler are free from residual hydrogen, have a smooth feel, good skin adhesion, good color and spreadability and resistance to acids and alkalis. The treated powders are useful in cosmetics such as powder formulations, oil-in-water and water-in-oil emulsions, anhydrous make-up and lipstick. Treatment can be effected with a linear reactive alkylpolysiloxane having substituted in repeating units in the backbone of the molecule both cationic and anionic groups, for example aminoethylaminopropyl and alkoxy groups. The organosilicon compound can be adsorbed and chemically bonded to the surface of the powder by heat treatment. The alkylpolysiloxane compound can have a degree of polymerization of from 5 to 100, preferably 10-15. A process for producing the treated pigment is also disclosed as are cosmetic formulations made with the treated pigment.