Copper-graphite block.
An example of the element Carbon

Copper graphite, This sells well on ebay, think this is used for motor brushes, about the strangest stuff I have ever seen, you'll have NO trouble convincing people it is some weird Roswell metal. Interesting thing you can do with it is cut out a narrowish bar of it place in a "quarter shrinker" and once zapped with enough juice makes about the most tough material i have EVER, come across! It is like something out of science fiction after that treatment. It can be pounded and beaten on an anvil like wrought iron when hot, but good tool steel, tungsten carbide drills, lasers, ceramic lathe bits and other means of parting it don't cut it until it is heated enough to almost melt/burn! Silicon carbide cut off wheels will grind is slooooly though.