Other forms: graphites
Use the noun graphite when you're talking about the mineral that's used to make pencil lead.
Graphite is a form of carbon that is most commonly found in pencils, although because it is a good conductor of electricity, it's also used in electrodes and batteries. Graphite can in fact be found in a wide variety of things, from a car's brake pads to industrial lubricants. The word graphite comes from the German Graphit, which was named by a mineralogist in 1789 from the Greek word graphein, "write."