Coal ore is found commonly underground embedded in stone. It is mainly used as a fuel in smelting metals such as iron and gold. The Ore is used directly as a Crafting Material instead of just the Coal which at the moment can't be extracted from Coal Ore.
Coal Ore is generated in large patches, one patch sometimes containing hundred blocks of Coal Ore. Those patches are mined fastest by first digging a way in, then spam-clicking while turning around.
Coal Ore is one of the few items that have to be mined with more than just one mouse click. Either you need to hold your mouse button, or you need to click about twenty times before the block breaks. The existence of this durability also points to a possible addition of tools that modify the mining speed.
One patch of Coal can become a resource that the player visits not once, but mines always that much he needs.
Coal Ore is an important Crafting Material. First, it can be crafted into Torches by adding Coal Ore to Wood. Then it can "smelt" Iron Ore/Gold Ore to Iron Blocks/Gold Blocks. You do this by Crafting Coal Ore with Iron Ore/Gold Ore in a ratio of 1:1.
|Iron Ore||Coal Ore||→||Iron Block|
|Gold Ore||Coal Ore||→||Gold Block|
|Iron Block||Coal Ore||→||Brushed Metal|
|Gravel, 2||Coal Ore||→||Asphalt|