The 4th largest known impact crater on earth is found in Siberia, called the Popigai Crater- where the diamonds which formed 36 million years ago upon impact have been mined for industrial use. This particular impact site happens to be on a graphite-bearing rock and sediment area, which instantly converted to diamond upon impact, creating one of the largest diamond fields in the world, and giving the crater the nickname Crater of Diamonds.

Read more about it on NASA’s Earth Observatory