Diamonds and coal are made from the same substance, carbon. They are both formed by heat and pressure, but the results are very, very different.
Coal burns and can be a source of energy, though it is not a very clean source of energy because it’s full of impurities. Diamonds have few impurities and won’t burn.
Diamonds on the other hand are among the hardest substances. They can be used in industrial applications for cutting metal and similar uses because they are so hard and immutable. Coal is soft and combustible. It is dirty and rubs off everywhere.
Diamonds are clean, translucent, rare and beautiful. Diamonds are highly valued, while coal is something we would rather not use if we had other choices, even for burning up in a fire.
Would you rather be a diamond or a lump of coal?