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.