An anonymous reader writes:
Nokia has developed a diamond-like coating material made from coal. The coating is very tough, but also smooth to the touch. It's also conductive and therefore antistatic, so it does not attract dirt easily.
To make the material electric current is fed through coal graphite. This creates plasma, which is directed towards a plastic casing by high-voltage electrodes. The coal ions penetrate the surface and bond to form an amorphous, diamond-like coating less than 100 nanometres thick. The process works at room temperature, meaning even cheap plastics can be coated this way.
Here's the patent application.