How are diamonds made out of coal?

A popular myth that has found its way around is that diamonds are made out of coal. The belief is so ingrained that it led to the birth of quotes like this: “A diamond is just a piece of charcoal that handled stress exceptionally well.” While the precious gem and the coal are not much different from each other, there is very slim chance that the former is born from the latter. Interestingly, the primary component of both materials is the same element: Carbon.

The origin of all the diamonds excavated so far traces back to before the Cambrian period, about 550 million years ago. The age of these diamonds is estimated to be between 1 billion and 3 billion years.

Diamonds are minerals surrounded by igneous rocks. Unlike the other gems, they are formed solely by carbon. The formation of diamonds requires immense pressure and ultra-high temperature. They are formed between 90 and 120 miles below the Earth’s surface where temperature is around 1000 degree Celsius. Since they are formed so far below, you may wonder how we could find them. They are brought to the surface by phenomenon known as deep source volcanic eruptions. 

It is such a rare occurrence, and hasn’t happened since it was recognized. Diamond is one of the two pure forms of carbon, the other being graphite. The carbon source of these diamonds is believed to be the carbon that was trapped in the planet’s interior at the time of its formation. Coal on the other hand is a fossil fuel, found no deeper than 2 miles below the surface. It is formed under high pressure as well, but from the fossils of living organisms. And the coal seams are sedimentary rocks while diamond blocks are, as mentioned earlier, igneous rocks. The sources of coal are the sediments of plants, and the earliest plants on Earth didn’t appear until 450 million years ago.

Other than deep source eruptions, the two other processes how diamond may be formed are subduction of tectonic plates and asteroid impacts. However, these processes also rarely involve coal. Coal could be present in the sites where they could happen, but the possibility is very low.

Fun fact regarding diamonds however; diamonds aren’t as rare as you might think. The reason why diamonds are so expensive is because there is a monopoly on them. Only the diamond industry, mainly De Beers Jewelers, is allowed to control the supply of diamonds. And when they can artificially manufacture scarcity, they can ramp up the prices all they want. In the end, it’s the people willing to shell out exorbitant amounts of cash for this pretty rock that allows for diamonds to be as expensive as they are.

When it comes to functionality, coal is certainly more useful than diamonds. Though diamonds require a more specific kind of procedure to form, their method of production is basically the same as that of coal; extreme heat and pressure. So maybe that’s why people call them the same thing in a sense, and they’re not half wrong.

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