The researchers studied different types of coal to see how their structures affect their quality for making coke. They found that coals with the same grade but different vitrinite reflectivities can produce different quality coke. They also discovered that inertinite in coal, which was previously thought to be unreactive, can actually be reactive. By looking at the fluorescence and reflectivity of inertinite, they can estimate how much of it can melt during processing. They also found that the structure of vitrinite in coals can vary depending on how reduced they are. This information can help classify coals based on their quality for coke production.