Diamonds are formed from coal.
Don’t believe that!
Since we are taught in school that both coal and diamonds are made of carbon, it is widely believed that a lump of coal can be transformed into diamond through intense heat and pressure. While this may be possible in principle, the fact is that the diamonds on Earth definitely did not originate in this fashion.
Coal, a fossil fuel, formed from the remains of prehistoric plants, a process that took many millions of years. Coal, as you would expect, is found at relatively shallow depths.
Diamonds, on the other hand, formed over one BILLION years ago, long before coal, or even land plants, existed. The creation of a diamond requires very high temperatures and pressures, conditions that exist only at a depth of approximately 100 miles beneath the surface of the Earth. Human beings would probably have never laid their eyes on a natural diamond would it not for the volcanic processes that bring them to the surface!
Diamonds begin their life as a pure form of carbon known as graphite. Coal could turn into diamond under the proper rare conditions (such as a lightning strike or asteroid impact), but the result would be impure and of poor quality.