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[–] riposte ago 

Yeah, it's not that old.

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[–] Lobotomy ago 

Gneiss rock you got there.

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[–] sweetholymosiah ago 

but... we walked with the dinosaurs? right?

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[–] cpebach 1 point 5 points (+6|-1) ago 

It's the sort of rock that most of us will just take for granite.

(Bah Dum Tss!)

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[–] MrPim 1 point 1 point (+2|-1) ago 

That's the shist.

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[–] cpebach 1 point 2 points (+3|-1) ago 

That shist is gneiss!

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[–] 7454122? 0 points 10 points (+10|-0) ago 

It doesn't look a day over 3,900,000,000

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[–] PoundSign_999 1 point 0 points (+1|-1) ago 

Absurd! I'm having nunavut!

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[–] Diamond_Deluge 0 points 2 points (+2|-0) ago 

and how do we know its 4b years old?

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[–] rwbj 0 points 4 points (+4|-0) ago 

Some minerals are the product of the radioactive decay of other minerals. For instance in really old rocks it's probably going to be uranium turning into lead. In a mineral where you can safely assume that any trace of one element is a product of the radioactive decay of another element you can simply take a sample of it, measure the ratio of the elements and determine its age to a phenomenally high degree of accuracy. For uranium lead dating - the accuracy is higher than 99%. And it doesn't have to be anything like pure uranium. Various minerals contain trace amounts of radioactive elements. Zircon and Uranium for instance. But that trace is far more than enough for dating.

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[–] TexasVet 0 points 3 points (+3|-0) ago 

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[–] Nutark 0 points 1 point (+1|-0) ago 

Jesus Christ Marie!

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[–] oedipusaurus_rex ago 

I said this all the time when I was taking mineralogy.

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