You walk into a fancy party. What is the oldest thing there? No, not your in-laws, or even your grandparents. It will be a diamond someone is wearing.
It's not completely clear how natural diamonds are formed, and although it is known they are made from carbon, scientists are not sure how carbon gets to the extreme depths at which diamonds are made.
Diamonds are formed very deep in the earth. The optimum depth for their formation is about 120 miles beneath the surface, in the molten mantle.
The temperature and pressure necessary for diamonds to crystalize are mind boggling: the temperature must be over 2,000 degrees Fahrenheit, and the pressure must be at least 690,000 pounds per square inch. To put that pressure in perspective, a 150 pound person exerts only about 3 pounds per square inch.
Temperature And Pressure
We would never know about diamonds were it not for volcanic activity, for that's what delivers diamonds from deep inside the earth to where we can get to them.
Theoretically diamonds can remain diamonds only at high temperature and pressure. In theory, at atmospheric pressure and lower temperature chemical changes are liable to take place that change diamond into graphite, similar to the stuff pencil leads are made of.
However, it has been calculated that even if this change were to take place it would take over ten billion years to happen.
Now back to the diamond's age. Scientists think diamonds may have been forming throughout earth's history.
Many have been found that are three-point-three billion years old. And the young ones are a mere one billion years old.