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Mysteries of Diamonds – Hard to Ignore, Harder to Form

Have you seen the classic movie Superman III? There is a scene wherein Clark Kent (Superman) picks up a lump of coal and presses it in his hands. Lo and behold! The massive strength of the man of steel converts it into a perfectly cut diamond and we all went, “WOW!”

Would it not be cool if we could take some big lumps of coal, apply ultra-high pressure and temperature to it, and get gorgeous diamonds? We would all be rich overnight. Unfortunately, converting coal to diamond can only happen in the movies. Then again may be the Superman can do it with his unreal superpowers.
Yup, that’s true – diamonds do not come from coal. They might be found in some coal mines somewhere, but there’s no way that coal might become diamond.
How do diamonds actually form?
For starters, let us understand that both coal and diamonds are made of carbon (though diamond is purer). Yes, you read that right. Both have the same basic material at their cores. However, while coal is only black with zero reflective qualities, diamonds come in a range of colors and have very high reflective indices.

It takes ultra-high pressure,approximately 50 Kilo bars, and extreme temperature, in excess of 1000 degrees Celsius, to form a diamond. Such pressures and temperatures are only possible deep in the earth’s crust – somewhere between 140 and 190 kilometers. There would have to be some form of carbon available deep down there, but that would not necessarily be coal.

Interesting Trivia: Diamonds were formed deep in the earth’s crust somewhere between 600 millionto 3.3 billion years ago. That’s means the youngest diamonds we hold in our hands today were formed way before the dinosaurs ruled the earth.

Actually, coal is rarely ever present that deep below the surface. Coal is usually found at just about 3.2 kilometers underneath the surface. Moreover, coal is formed from plant / vegetation sediments at much lower pressure and temperatures.

Luckily, that would not be required as the diamonds normally get pushed closer to the surface due to a special kind of volcanic eruptions or earthquakes. Now don’t go about thinking that every time there is a volcanic eruption, there will be diamonds spewed out of the earth for the picking. To the contrary, there is no recorded recent volcanic eruption that has brought diamonds to the surface.

That’s because the diamond bearing crust (or mantle as it is correctly known) is much deeper than most currently active volcanic tubes. In other words, diamond bearing regions of the earth came to have those diamonds hundreds of thousands of years ago when there were massive and deep crust volcanic activities thereabouts.

Well, that’s all about how diamonds are formed and come to the surface of the earth to reach us. Next up, we will take a look at the long history of man’s love with this most precious of stones.

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