Petrographic studies are commonly used to categorize the potential utilization of coals. Eleven coal samples from the Jharia coalfield (JCF), India, were studied using petrographic techniques to investigate maceral content, reflectance, and textural characteristics. Multiple test samples of each coal were slowly oxidized under controlled laboratory conditions from an ambient temperature of 30°c to 300°c to investigate the morphology of oxidized coals. The petrographic characterization of coals before and after oxidation showed significant changes in both morphology and vitrinite reflectance. The oxidation of coal particles produced three predominant textural changes: particles with homogeneous change of reflectance (HC_v), particles with oxidation rims (OR_v), and particles with no changes were observed (U_v), respectively. These textural characteristics were used to indicate how particles had interacted with oxygen at low temperatures during the early stages of oxidation. The morphological classification developed provides an alternative method to confirm the susceptibility of a coal to spontaneous combustion. Conventional thermal parameters such as crossing point temperature (CPT) were unable to identify the coals prone to spontaneous combustion. However, certain petrographic parameters could be combined with CPT values to provide a much more accurate measure for susceptibility to spontaneous combustion.

岩石学研究通常用于对煤炭的潜在利用进行分类。使用岩相学技术研究了印度Jharia煤田（JCF）的11个煤样品，以研究其矿物含量，反射率和组织特征。在受控的实验室条件下，从30°C到300°C的环境温度下，将每种煤的多个测试样品缓慢氧化，以研究氧化煤的形态。氧化前后煤的岩石学特征表明形态和镜质体反射率都发生了显着变化。煤颗粒的氧化产生三个主要的组织变化：反射率均一变化的颗粒（HC _v），氧化边的颗粒（OR _v）），观察到没有变化的颗粒（U _v）。这些质地特征被用于指示在氧化的早期阶段，颗粒如何在低温下与氧气相互作用。建立的形态学分类提供了另一种方法来确认煤对自燃的敏感性。常规的热参数，例如交叉点温度（CPT），无法识别易于自燃的煤。但是，某些岩相学参数可以与CPT值结合使用，以提供更准确的自燃易感性度量。