a solid lubricant and composition useful for lubricating the flanges of locomotive wheels , railcar wheels , rail tracks and in applications where it is desirable to reduce friction when metal contacts metal . the solid lubricant having from about 25 % to about 70 % by volume of a biopolymer polymeric carrier , about 5 % to 75 % percent by volume of organic and inorganic extreme pressure additives , about 0 % to 20 % by volume synthetic extreme pressure anti - wear liquid oil , and about 0 % to 1 % by volume optical brightener .