Coal samples from the Witbank Coalfield in South Africa were analyzed using electron spin resonance to study the formation of inertinite macerals. By looking at the ESR spectra and the H/C ratio, researchers found that the inertinite-rich samples had a higher radical content, indicating they are more aromatic. This suggests that the dominant inertinite macerals formed through the charring of plant matter. The ESR spectra for the inertinite-rich sample showed pronounced electron mobility and exchange interactions, supporting the idea that specific inertinite macerals like fusinite and semifusinite were present in the samples.