Why are diamonds so rare and valuable?

Lots of people love sparkly, pretty things – especially precious stones, like diamonds. But who decides which stones are precious? And what makes diamonds so special? We asked geologist Marc M. Hirschmann to help us find the answer. Got a priceless question? Send it to us at BrainsOn.org/contact, and we’ll help find a jewel of an answer! See omnystudio.com/listener for privacy information.