A solid lubricant additive for resin-bound friction lining mixtures contains manganous sulphide (MnS). The additive further optionally contains other sulphides, carbon carriers such as graphite and coke, phosphates and/or oxides. The additive results in the adjustment of the coefficient of friction and wear in friction lining materials. The additive may be advantageously employed in asbestos-free and lead-free friction lining mixtures in heavy-duty friction parts as used in brakes, clutches, synchromesh gears.