A composition of matter for use in tribological applications, such as in mechanical seals, bearings and other sliding or rubbing components, which provides good durability and wear characteristics. The material is used in the "softer" one of two relatively sliding members which are in, or may come into, contact with each other during the relative rotation of one of the member s relative to the other. The material is a carbon or carbonaceous formed material, such as is normally used in the manufacture of a primary seal ring in a mechanical seal, and comprises an additive compound which contains at least one compound from a group consisting of neodymium fluoride, praseodymium fluoride, gadolinium fluoride and lanthanum fluoride.