craton: “an old and stable part of the continental lithosphere, where the lithosphere consists of the [Earth’s crust and] uppermost mantle.”

https://en.wikipedia.org/wiki/Craton

I looked this up after learning about cratons in an article I listened to this morning (http://www.economist.com/news/international/21717369-production-worlds-most-valuable-gem-may-be-about-peak-report-de-beerss).  Excerpt from the article:

Natural diamonds—as opposed to the synthetic ones mostly used in industry—were formed more than 1bn years ago deep below cratons, the oldest part of continents. There, between Earth’s core and its crust, the pressure was high enough and the temperature low enough for carbon to crystallise into its hardest form. There diamonds would have remained were it not for molten rock rushing through the mantle and drawing diamonds, garnets and other minerals with it, like a furious river pulling dirt from its banks, before erupting through Earth’s surface faster than the speed of sound.

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