Pencil "lead" is not made of the toxic metal lead. It is a mixture of graphite (a form of carbon) and clay. The ratio of graphite to clay determines the hardness of the pencil lead. More graphite results in a softer, darker mark, while more clay results in a harder, lighter mark.
Pencil lead is :
Asked in UPPCS Prelims 1994 · Topic: Carbon and Its Various Forms (Amorphous forms of Carbon: Coal, charcoal, coke, lamp black)
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