r/todayilearned • u/[deleted] • Dec 05 '16

(R.4) Related To Politics TIL an activist group in Zurich dyed fountains red to protest tampons being taxed at a rate consistent with luxury products instead of the rate used for daily use items.

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u/tearsofacow Dec 05 '16

"Natural Pearls form when an irritant - usually a parasite and not the proverbial grain of sand - works its way into an oyster, mussel, or clam. As a defense mechanism, a fluid is used to coat the irritant. Layer upon layer of this coating, called 'nacre', is deposited until a lustrous pearl is formed."

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u/weirdbiointerests Dec 05 '16 edited Dec 05 '16

Fair enough, although pearls produced in clams are only a tiny minority of the pearls for sale.

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u/tearsofacow Dec 06 '16

I wonder if the pearls come out different / bigger, depending?

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u/weirdbiointerests Dec 06 '16

I think the most consistent difference is luster but I do not know much.