According to the composition of coal and rock and the average brightness strength reflected by it, it can be divided into four types of coal and rock: bright coal, semi-bright coal, semi-dark coal and dim coal.1. Bright briquetteIt is the most burnish stratification in the coal seam.It is mainly composed of vitrinite and bright coal (> 80%).Because the components are relatively uniform, they often show a uniform or not obvious lineation structure.Endogenous crack development, brittleness, easy to break.The quality of bright briquette is the best and the coal is the best for metallurgical coke.2. Semi-bright coalBright coal and vitreous coal account for the majority (50%~80%), contain dark coal and silk charcoal.The gloss strength is slightly weaker than that of the bright briquette.Due to the alternations of various macroscopical coal and rock components, the structure is often banded.With angular or stepped fractures.3. Semi-dark coalThe content of vitreous coal and bright coal is less (50%~20%), while the content of dark coal and silk carbon is more, the luster is relatively dim, often with a banded, linear or lenticular structure.The hardness, toughness and specific gravity of semi-dark briquette are large, and the quality of semi-dark briquette is mostly poor.4. Dull briquetteVitreous coal and bright coal content is very few (< 20%), and dark coal is main, sometimes contain more silk charcoal.Dim luster, no stratification, massive structure, linear or lenticular structure, dense and hard, great toughness, significant.The quality of the dimmed coal is mostly poor, but the quality of the dimmed coal with many crusts is better and the specific gravity is small.