Popigai crater

Popigai crater is an impact crater in Siberia, Russia. It was formed when a meteor struck the Earth about 35 million years ago.
There are many diamonds under the crater. The diamonds were made when the high pressure of the meteor hitting the ground compressed the graphite. 
Even though there are many diamonds, mining is not considered to be profitable. That is partly because the mine is in a place far from people. Perhaps it is more because its diamonds are only industrial quality, and they can be made more cheaply by artificial means.