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If I understand correctly, graphite is made of sheets of carbon.

Graphite layers (from Wikipedia)

And when I write with a pencil, sheets of carbon slide off the end of the lead. Does that mean there is an optimal orientation of the graphite where the sheets are parallel to the paper? Does this make a difference?

jkd
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1 Answers1

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Wikipedia says "Modern pencil lead is most commonly a mix of powdered graphite and clay ... Low-quality amorphous graphite is used and sourced mainly from China." "Amorphous" (roughly) means that something is not a single crystal, so it seems as though the sheets in pencil lead are broken up into (microscopically) tiny, randomly-oriented pieces, so they are not oriented in any particular direction.

tparker
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  • Does amorphous mean that the graphite does not have an orientation? It's just randomly arranged in pencils? – jkd Oct 23 '17 at 00:05
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    @jakekimdsΨ Basically, yeah. Technically it means that there isn't any "long-range translational symmetry breaking", which basically means that at tiny length scales the atoms can be locally arranged like an ordered crystal with all the sheets aligned, but the local alignment points in a different direction in different places, so if you zoom out to macroscopic length scales, then the local orientation vectors all average out to zero. – tparker Oct 23 '17 at 00:25