Pencil lead

Pencil lead comes from graphite, a carbon-based compound similar to charcoal. Elemental lead is toxic to humans and is no longer used as the 'lead' in pencils. I entice you to take a look at the Periodic Table of the Elements under Pb to learn more about it. Among other effects, it causes brain damage in young children. Since the change you no longer have to worry about sucking on your #2 pencil during an exam.

Granite is a kind of rock, very hard, far too hard to be used as pencil lead. It is primarily made of silicon (Si in the periodic table).

-Nick