This is a collection of 0.02, 0.03 and 0.04 carat solitaire diamonds weighing in total 5.36 carats. Credit: Swamibu/Wikipedia

There might be a quadrillion tons of diamonds 100 miles below Earth's surface.

But the farthest we've traveled is 7 miles down, so how could we know that?

Credit: American Chemical Society and PBS Digital Studios