Which allotrope of carbon is used as a lubricating agent & also as a moderator in nuclear reactor?

Graphite usually occurs in flakes in metamorphosed rocks rich in carbon, but it can also be found in veins and in pegmatites. Where large deposits are found it is mined and used as an industrial lubricant and for 'lead' in pencils. Graphite is a polymorph of the element carbon. , Graphite is a good conductor of electricity.,a very good lubricant,opaque, and  crystallizes in the hexagonal system.Somewhat of a surprise is that at surface temperatures and pressures, Graphite is the stable form of carbon. Graphite has a sheet -like structure where the atoms all lie in a plane and are only weakly bonded to the graphite sheets above and below. It may seem strange that one of the softest minerals and also a very slippery lubricant is the high-strength component in composites used to build automobiles, aircraft, and of course golf club shafts. It is also used as a moderator in nuclear reactor.