I just felt like making a whimsical robot character with a hint of shading. So...

Coal-bot uses his powerful steamshovel-like jaws to chew into coal and redstone deposits after locating them with his night vision optical sensors. Using the energy stored in redstone to generate intense heat and pressure in his gullet, he converts coal into diamonds and ejects them out a retractable trapdoor in his backside. His tank-like treads help him move over rough terrain. The red light on his head flashes to warn organic miners that he is in the area. Standing in front of him to adjust his controls (while he is in motion) is a lot more dangerous than following behind collecting his extremely hot diamond droppings. WARNING: Eating lapis lazuli gives him digestive problems. Best not to stand behind him when he has ingested it.