a continuous method of removing volatilizable organic composition from particulate mineral composition comprises heating the organic composition contaminated mineral particles in a rotating drum and exposing the particles to said hot gases to volatilize the organic composition from the mineral particles while advancing the particles counter - current to the direction of hot gas flow , removing a gaseous composition from the drum comprising a mixture of the gases of combustion , volatilized organic composition and airborne fine mineral particles , separating the fine mineral particles from the hot gases and volatile volatilized organic composition returning the separated fine mineral particles into the drum near the hot end , mixing the fine particles with the coarse mineral particles advancing toward the hot drum end , continuing to heat the mixture of fine and coarse mineral particles until the concentration of volatilizable organic composition is less than about 100 parts per million , and recovering a mixture of coarse and fine mineral particles adjacent said first drum end . the invention includes a preferred apparatus for carrying out the process .