Diamonds, which form eight-sided crystals called octahedrons, can be billions of years old, Dr. Harlow said. “Lots of ancient diamonds that have been down there for close to two billion years will still look like octahedrons,” Dr. Harlow said. As for very rare red diamonds, the theory is that they are the result of cavities of a very uniform size. If these elevators are too slow, however, that leaves diamonds vulnerable to being dissolved in the fluid they are brought up in. “Once they are near Earth’s surface, it is very difficult to get rid of diamonds,” Dr. Harlow said.

Source: New York Times June 12, 2017 13:30 UTC