There is an ASTM classification, which is an American society. According to these principles, coal is divided into 4 main types, which directly depends on the stage of transformation of the material:

• lignium (alternative name - brown coal);
• subbituminous;
• bituminous (aka hard coal);
• anthracite.

Let's not go into details and say that the main difference between these types is the carbon content and the amount of heat generated. If these indicators are minimal for lignium, then anthracite is already considered the most efficient, and therefore valuable, type of coal.

If we look at coal from an economic point of view, then fossils are considered in 2 categories - thermal coal and coking coal. The main difference is the area of application for which certain categories of coal mined in the earth's layers are intended.