Calcium carbonate is actually a mineral that is the main component of the shells of marine animals and fossilised plankton. Due to the way they're formed, as sedimentary rocks, limestones are rich in calcium carbonate (not the other way around).
Chalk is a type of limestone, and all chalk is indeed made in big part of plankton and microscopic shell bits.
It is especially rich in coccoliths, which are plaques of calcium carbonate organised in a sort of ball, making up coccolithophoridae (I'm only putting this here because I love saying coccolithophoridae).
Bonus funfact: sometimes, limestone used in construction has little gastropods in it for instance.
Well there we go, learning a thing
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Though Google mentioned some chalk is made from gypsum, which is apparently calcium sulfate dihydrate. Which may well be more plankton skeletons for all I know
Ah yes, good point I forgot to mention, chalks used today in classrooms etc are made of plaster, which is made of gypsum, and that's not plankton!
(I don't mean to come across as pedantic, I just had the "oh hey I know this" reflex kicking in x)
Lol no you're good - it was interesting :) tbh when I first looked into it I thought gypsum was the one made from plankton so I'm actually glad to have that corrected. Plus I'm literally basing this off Google and it's always interesting to have someone who actually knows a thing expand on it
From an article titled: should you be worried if you're eating chalk?"
"While chalk is minimally toxic, not poisonous in small amounts, and may not hurt you, it's never a good idea to eat chalk. A pattern of eating chalk is a different story, however. Eating chalk often can disrupt your digestive system and cause damage to your internal organs."
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Apparently this is a more common problem than I ever realized
Chalk is a type of limestone, and all chalk is indeed made in big part of plankton and microscopic shell bits.
It is especially rich in coccoliths, which are plaques of calcium carbonate organised in a sort of ball, making up coccolithophoridae (I'm only putting this here because I love saying coccolithophoridae).
Bonus funfact: sometimes, limestone used in construction has little gastropods in it for instance.
`
Though Google mentioned some chalk is made from gypsum, which is apparently calcium sulfate dihydrate. Which may well be more plankton skeletons for all I know
(I don't mean to come across as pedantic, I just had the "oh hey I know this" reflex kicking in x)
"While chalk is minimally toxic, not poisonous in small amounts, and may not hurt you, it's never a good idea to eat chalk. A pattern of eating chalk is a different story, however. Eating chalk often can disrupt your digestive system and cause damage to your internal organs."
`
Apparently this is a more common problem than I ever realized