Discussion on identification standard of coal-measure graphite

The identification and classification of coal-measure graphite are the precondition and basic work of mineral geological exploration, as well as resource exploitation and utilization. The preparation of identification standards of coal-measure graphite should follow the principles of science, systematicness, applicability and operability. Coal graphitization and coalification is a continuous progression plus jump process, and the characteristics of coal-measure graphite, including the step evolution of macromolecular structure and the heterogeneity of material composition, leads to the complexity of ore identification. In order to establish the scientific and practical identification standards, and from the study of metallogenic mechanism and the demand of resource evaluation, coal-measure graphite was divided into three types: No.1, No.2 and No.3, according to the graphitization degree of the ore as a whole ranges from high to low. On the basis of the previous work, more than 110 groups of measured data were added, and the identification index system of coal-measure graphite composed of the preliminary and precise identification indexes was modified and perfected. The preliminary identification indexes, including the volatile yield V_daf and the maximum reflectivity R_max, are used to roughly distinguish coal and coal-measure graphite in the stage of resource evaluation and geological exploration. The precise identification indexes, including the interplanar spacing d₀₀₂, its equivalent graphitization degree G, and Raman spectrum parameter R₂, are used to accurately distinguish coal and coal-measure graphite, and to classify the types of coal-measure graphite. Besides, the classification indexes of coal-measure graphite were determined based on the statistical analysis results of the measured data of over 500 groups of samples from the main coal-measure graphite mines in our country, including No.1 coal-measure graphite with 0.335 4 nm ≤ d₀₀₂ < 0.338 0 nm (G > 0.70) and R₂ < 0.50; No.2 coal-measure graphite with 0.338 0 nm ≤ d₀₀₂ < 0.340 0 nm (G>0.50−0.70) and R, 0.50−0.60; and No. 3 coal-measure graphite with 0.340 0 nm ≤ d₀₀₂ < 0.344 0 nm (G>0−0.50) and R, 0.50−0.60. Thus, an identification template of coal-measure graphite was established based on the above indexes, which was practical and operable according to the test data of samples from the main coal-measure graphite mines.