Abstract: A method and device for mineralization of carbonaceous materials, for determining trace concentration of chemical elements in foods, fodder, plant, and animal tissues and other materials. The method can also be used for determining the structure of the mineral skeleton of carbonaceous materials or for preparing ash of carbonaceous materials for various technological uses. The method includes heating a specimen to a temperature ranging from 300.degree. to 400.degree. C. for 6 to 20 hours at atmospheric pressure in a stream of oxygen, at a rate of 0.03 to 0.15 ml.s.sup.-1.g.sup.-1 of the specimen. A gas with a higher oxydative strength than that of oxygen is added to the stream of oxygen, said gas being selected from the group consisting of ozone, nitrogen oxides, chlorine and mixtures thereof such as an ozone-nitrogen oxides mixture, chloroxides of nitrogen, in an amount of 1 to 6 volume percent.