How To Distinguish Quality Of Coal

in the current post I discussed about how to distinguish low-calorie coal and high calorie coal directly. in our survey activities are often difficult to distinguish coal, where coal low calorie and high calorie coal which, in fact we can distinguish both cases in the following manner:
 1. Hardnes coal
     coal with low calorific value usually has a relatively low violent or vulnerable, while coal with high calorific value is usually louder than the low-calorie coal. 
2. Scratch
    We can differentiate with nails scraping the coal is found, if the scratch and dull brown color, it means that coal is a low-calorie, but if the scratch is black means high calorific coal. 
3. Sheen
    We can differentiate with the sheen of the coal, soil and dull sheen if means lower calories, but if the oil sheen - gloss glass means high calories 
4. Heavy coal
   Usually low-rank coal is more severe in comparison with high calorie coal, because the water contains a lot of low calorie and its formation is not perfect.
If the four points above have not made your crested black macaques, there is a danger that the most appropriate way."Bring your coal samples to the laboratory for the meticulous", it is the best way of four points above
Good luck, success for you ................