The dwarves use this curious metal like coal, and their refineries and smithies consume vast quantities of them. Thus, one could say that heatstones are a central part of dwarven life. Heatstones become the replacement of wood and serve the subterranean race in all manners. It is mined primarily for heating, illumination and cooking.
Heatstones are a special kind of metal. If one struck them with a very hard metal mithril, at the barest minimum they would produce intense heat.