For some reason, people think that coal + pressure = diamonds. The prevalent theory is that if I apply several thousands of tons of pressure to a lump of coal, I’ll end up with a lump of diamond. Hey, it worked for Superman, didn’t it?
Yes, yes it did. It shouldn’t have, but it did.
So, what gives? Where did this myth come from, how is it not dead yet, and where do diamonds come from if not from coal?? Calm down, you information-hungry knowledgemongers. Let’s start with where coal and diamonds actually come from, and we’ll see if we can get to the bottom of who put the two together and how it became part of the universal bank of misinformation I like to call “common nonsense.”
Where Coal Comes From
In a word, plants. During their development, planets goes through a hot, swampy, gassy stage. Like planetary puberty. Y’know what? The World Coal Association tells the story much more eloquently than I, so I’m just going to quote them. Take it away, WCA!
The build-up of silt and other sediments, together with movements in the earth’s crust – known as tectonic movements – buried swamps and peat bogs, often to great depths. With burial, the plant material was subjected to high temperatures and pressures. This caused physical and chemical changes in the vegetation, transforming it into peat and then into coal.
Smooshed coal doesn’t make diamonds, but smooshed plants do make coal.
So basically, plants and their swamps got buried beneath several layers of rocks and stuff, and over time, the pressure and heat turned them into something called peat, and then into coal. It’s worth noting that the energy we get from burning coal is the very energy that the plants absorbed from the sun through photosynthesis during their lives.
How Diamonds Are Made
Okay. So if diamonds don’t come from coal, where do they come from? They’re actually made of tightly compressed carbon molecules. According to the Smithsonian:
Diamonds are formed deep within the Earth about 100 miles or so below the surface in the upper mantle. Obviously in that part of the Earth it’s very hot. There’s a lot of pressure, the weight of the overlying rock bearing down, so that combination of high temperature and high pressure is what’s necessary to grow diamond crystals in the Earth.
Geophysicist and Fulbright scholar Stephen E. Haggerdy says the temperatures must reach about 1,500° Celcius (~2700° F), and the 50 kilobars (5 million Pascal Units, or 5 million Newtons per square meter. Hey, I’m just as lost as you are right now). This heat and pressure forces carbon atoms to pack together as tightly as possible, thus forming a super-organized, super-dense kind of lattice type structure. And thus, diamonds are born. Don’t believe me? Watch this video from National Geographic. Because the first rule of getting information on the internet is “Always Trust YouTube.”
It’s easy to see how people think diamonds are made from coal, since they are made from compressed carbon atoms, and coal is almost completely composed of carbon (along with hydrogen, sulfur, oxygen, nitrogen, and some other stuff).
So there you have it. Coal is mostly carbon, diamonds are made of carbon, but this is one case where A + B ≠ C. Now ponder that while I go tell my friend Kimberly that she was named after diamond-toting lava.
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