Not all coal is made equally, the blacksmith coal is different from heating coal, and it comes in pea size to about an 1" dia chunks. The differences in the coals is sulfer content and a few other impurities. Heating coal has a HUGE amount of sulfer so much so that the smoke rolls of VERY yellow and is Awful for forging blades as it can impart more sulfer into the metal's recipe , Forging coal smoke rolls off slightly yellow and Metalurgical Coal is the cleanest and most expensive coal it burns clean and slightly greyish white smoke. I use only "Pocahontas Slack" Forging coal, I pick it up a blacksmith hammer-ins (ABANA) and festivals around my state. Do a google search for pocahontas slack you'll come up with all kinds of suppliers. The last time I bought it was 06/02/08 and I got 300 lbs for right at $90.00 US. Or about $15.00 per 50# bag.