Reflectance variation with rank

The conversion was highest for coals in a narrow Ro max range of between 0.65 - 0.70. Cudmore s data on Australian coals also appears to exhibit a maximum when reflectance data is plotted against conversion (8). It is difficult to interpret this data because of the large variation in the vitrinite and reactive semi-fusinite content of these coals. The reactivity of vitrinite and reactive semi-fusinite would be expected to vary with rank but to different degrees. For several of the lower rank coals vitrinite is only a minor component of the coal. 

Seam correlations, measurements of rank and geologic history, interpretation of petroleum (qv) formation with coal deposits, prediction of coke properties, and detection of coal oxidation can be deterrnined from petrographic analysis. Constituents of seams can be observed over considerable distances, permitting the correlation of seam profiles in coal basins. Measurements of vitrinite reflectance within a seam permit mapping of variations in thermal and tectonic histories. Figure 2 indicates the relationship of vitrinite reflectance to maximum temperatures and effective heating time in the seam (11,15). 

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