xkcd

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submitted 2 weeks ago by [email protected] to c/[email protected]

49 comments fedilink hide all child comments

I have to pay with paper money.

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[–] [email protected] 78 points 2 weeks ago (13 children)

Sidewalk chalk isn't made of chalk anymore?

TIL: It's made of calcium sulfate, i.e. gypsum, the same stuff that goes into drywall, as opposed to calcium carbonate, i.e. rock chalk.

[–] [email protected] 21 points 2 weeks ago (2 children)

Well, it certainly isn't made of sidewalk.

[–] [email protected] 5 points 2 weeks ago (1 children)

Unless your sidewalks are made of gypsum.

[–] [email protected] 7 points 2 weeks ago

If there are, they won't be for very long.

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