Story of an atom: diamond

This is the third part of a story told to me by a Carbon atom in my brain. It started with her tale of how she ended up on earth, followed by an inside view of the Carbon cycle.

So like I said, I’ve fallen into this pattern of cycling around different places, occasionally going underground for a bit. One time I got buried was really special. Just… just a really *deep* experience, you know?

It started off as normal, I was in a bunch of organic matter that’d settled onto the bottom of the sea. Things got slowly hotter and more squashed, but this time it just didn’t stop. Things started falling apart – everyone got antsy and wanted to move around, some atoms badly wanted to escape. The organic gunk I was in broke down. Lots of water started coming out and disappearing upwards, eventually there was just us carbon atoms left. Lots of other atoms around us too, of course, lots of silicate minerals – big structures dominated by Silicon and Oxygen, all in rigid ranks. It got so hot and pressured that even they couldn’t cope and had to start rearranging themselves to get more comfortable. Some minerals just disintegrated and the atoms had to find other minerals to join1. I’d never experienced this before – I’d never been  buried so deep.

You know when you’ve drunk too much coffee and you’re stressed? You feel like you’re vibrating really fast but you’re quite uncomfortable and you feel stuck. Same with us atoms in the deep earth. One way to cope is to try and help each other. Take us Carbon atoms in that organic lump. At first we were just jumbled up in a heap, but eventually we sorted ourselves out a more comfortable arrangement – we got together in lots of groups of six, all joined up but flat. If we stacked up like this then things weren’t too bad 2. But it just kept getting more extreme. Eventually every single mineral changed, even quartz – I’ve never seen that before or since 3.

Things kept getting more extreme. All around us atoms kept shuffling around into new configurations that were more comfortable. Hydrogen was very uncomfortable, it became harder and harder for it to find a place in these new arrangements of Silicon and Oxygen and more and more it joined with Oxygen and disappeared upwards. Eventually, some of us Carbon atoms broke up and starting moving upwards in a liquid4.

We travelled a long way like this (but were still very deep) when suddenly: it happened. There was this crystal of carbon – the most amazing thing. You call it a diamond. I’d always been a bit snooty about atoms all locked together in a mineral – fancied myself as a free spirit. But I so wanted to join in this crystal of just carbon. The other Carbons beckoned me in and at first I couldn’t see how it would work. When I’ve been with carbon before, I was joining with 3 other carbons in a flat plane. In this crystal all 4 of my bonds were joined, each with another Carbon. Not just flat too. I only managed to squeeze myself in because we were so tightly squashed together and buzzing around so much 5.

Once I was properly in there, I didn’t mind the conditions. We felt so strong, all together, bound so tightly. After a while I started to lose myself – no more ‘me’, only ‘us’. I was merging myself into a greater thing. One great collective of Carbon, perfectly happy in one eternal unchanging moment….

Sorry, drifting off there. Amazing times, so special. It couldn’t last though: diamonds aren’t forever, not really. The first sign of trouble was when the rock around us started to melt. We ignored it, but suddenly the whole area around us started shooting up through a big crack! The pressure dropped incredibly quickly – we were in a panic because it felt like we might start breaking up – could we stick together in these new conditions? Luckily we quickly cooled as well, making it easier for us to stay together6.

We soon got used to the new conditions – we were still underground after all – and we remained strong, ready for anything. It was a rude surprise when the rock around us got crushed up and we saw daylight for the first time. We were having a lovely time bouncing those photons about through us when this human hand grabbed us and put us in the dark again.

We were still together through all of this, which made what happened such a sudden shock. We were whipped out of the bag and put in a funny metal box. All the air around us disappeared and then ZAP! A huge beam of light hit us. Hit me! There was so much energy that a bunch of us got blown apart, all our bonds broken. There I am, alone and floating in space, just I was in my first memory. I soon hit some weird thing and ended up back here on the surface, going through the same old cycles7. For a while it all seemed so shallow, so temporary, so lonely. I’ve talked to other Carbon atoms about it, but none of them know what I’m talking about.

Still it’s been nice talking to you about it. It looks like you’re about to break up this molecule I’m in, so I’ll be off soon, back out into the atmosphere. Who knows where I’ll end up next!

No atoms were harmed in the making of this story.

Notes:
1. This is the process of metamorphism, where minerals in sediment change into new ones
2. these are graphite layers. Jumbled organic carbon turns into more structured graphite when metamorphosed
3. this must be a subduction zone – quartz is stable down to 70 kilometres depth when it starts to change to coesite. Our atom is entering deep into the earth’s mantle
4. metamorphic reactions in a subducting slab often produce water, which moves upwards, sometimes as part of a silicate melt (e.g. magma)
5. diamond only grows under special conditions
6. diamonds reach the (near) surface in kimberlites – magma that very quickly moves up from the deep earth
7. Sounds like the diamond was studied by some geochemists. Some mass spectrometers use lasers to sample the isotopic composition of the Carbon

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