Did you know that coal does not actually form diamonds? No matter how much pressure and heat you apply to a piece of coal, it will not transform into a diamond. So how is it that we got all of these sayings about turning coal into diamonds? Part of it has to do with a conflation between coal and diamond mining, and the way both coal and diamonds are formed in the earth. Both of these are made up primarily of carbon. In fact, diamonds are carbon in its purest form, arranged in a very unique and specific chemical way that creates the unique hardness of a finished piece.
So, how are diamonds formed? It does still take an intense amount of heat and an enormous amount of pressure. They are formed deep beneath the earth, usually as a result of deep surface volcanic eruptions, which push the carbon deposits to a higher level of soil. There they remain trapped, where they will continue to develop and bond under the pressure. The pressure changes the way that the carbon atoms deal with one another.
Coal, on the other hand, is formed through a complex process that is made up of lots of decaying organic matter. Dying plants and animal deposits become part of the coal itself, along with carbon and traces of mercury. It is the reason that coal is such a toxic substance to inhale, and why coal mining continues to be a dangerous profession. Coal has carbon in it, but also houses many other elements that cannot be strained out or transformed. It is because of this that coal cannot become diamonds. No matter how much they are treated with heat or intense pressure, they are not going to become the shining, beautiful diamonds we know and love.
Small diamonds have even been found in outer space, inside of meteorites. These meteorites, of course, contain no traces of coal or the elements that make up coal – just the pure carbon that creates the most beautiful and chemically perfect diamonds in the world (or, in this case, out of it).
Diamonds are something all their own, and not all carbon is equal. The widespread myth that coal can be turned into diamonds can make for some rather poetic turns of phrase and some powerful metaphors, but is, overall, not factually accurate. Diamonds are much purer than the diverse chemicals that make up coal.