What are black lumps that burn?

Black lumps that burn could refer to several materials, but commonly they are associated with coal or charcoal. These substances are carbon-rich and are used as fuel for heating or cooking due to their ability to produce a steady heat when ignited. In some contexts, they might also refer to certain types of wood or other organic materials that have been charred or burned. If found in an unusual context, they could indicate the presence of hazardous materials or waste.