Contrary to general belief, not all coals are alike. As evident from the pictures below, they all look and burn differently. The source and the formation of the coal directly controls & specifies the coal attributes. For eg. a mine�s location based on the geological history of the area and how the coal was formed back in history can impact & determines the Coal�s GCV ( Gross Calorific Value ).

It is possibly very hard to imagine how different our world was 600 to 300 Million years ago. Back in the period that coal is formed from was dominated by plant live and very little animal life. The other factors were higher oxygen content in the atmosphere along with a much moister environment. Based on these factors being in place it is not that hard to visualize lush and plentiful plant growth. So in some areas large accumulations of plant material would accumulate on the ground and create bogs were the material was covered by water or other plant material and did not completely break down. With geological changes other materials were deposited on top of these bogs and with depth and pressure turned to rock. The pressure dries the material, compressed it and eventually turned it to Coal, a flammable rock. This way coal is formed & tends to be in veins and stratified. Various conditions created various qualities of coal deposits that are presently mined for energy.