Under the Microscope: Graphite

Originally posted here: https://www.mcgill.ca/oss/article/technology/under-microscope-graphite

Pencils do not contain any lead, and they never did! The mistake in terminology can be traced back to the ancient Romans who drew lines on papyrus using pieces of actual lead, all the while not realizing it was incredibly toxic. Considering its toxicity, it’s really good that pencils never did contain lead. Could you imagine how much a child could ingest while chewing on their pencil?
So, what is the dark stuff inside pencils if not lead? It’s actually a mixture of graphite and clay. Graphite is literally named for its ability to leave marks on paper. It comes from the ancient Greek word graphein, meaning to draw.
If you’re ever especially stressed during an exam, you could always try squeezing your pencil tip. Under enough pressure, and at high enough a temperature, graphite turns into diamond, and I expect if you manage to manually make a diamond, you won’t mind a bad exam grade as much.
But besides allowing students to take exams and artists to draw, graphite serves an important role in batteries, particularly in lithium-ion batteries, due to its high conductivity.

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