Abstract: In accordance with the present invention a pyrolytic boron nitride compact having an electrical resistivity smaller than about 10.sup.14 .OMEGA.-cm is formed by the process of introducing a feed gas of gaseous boron halide and ammonia at a suitable ratio into a furnace heated to a temperature between 1600.degree. C. to 2200.degree. C. with the furnace containing a substrate of graphite to form a deposit of pyrolytic boron nitride upon said substrate, substantially simultaneously introducing a hydrocarbon gas into the furnace to form a codeposit of carbon in the crystal structure of the pyrolytic boron nitride deposit, controlling the mole fraction of said hydrocarbon gas to limit the concentration of carbon to less than about 3 wt % of the pyrolytic boron nitride composition.