2.1 Opening up a smartphone

So, this week we’re going to truly look at the geology that’s in your pocket. We’re going to look at one of these. This is my old iPhone, and it’s crammed full of technology. Now, a lot of the things that go into that technology came from the Earth, so that means it’s also crammed full of geology.

So, the first thing we’ve got out is the screen. And, like a lot of things we’ve seen so far in the course, the screen’s just glass. Glass is made of quartz – silicon dioxide – just ordinary sand. But, like a lot of modern iPhones, this glass has also been strengthened. And to do that, they add a few things. One of them is aluminium oxide. And that comes from bauxite – this kind of stuff. And this is a heavily weathered rock that you find in a lot of tropical places. If we turn it over on the back again, we’ve got bits like this. This, again, more aluminium. This is some of the shielding that prevents electromagnetic interference. More bauxite.

But if we keep going deeper …

So, this next bit’s a little bit fiddly, but let’s see if we can get off this shield.

What’s that shield for?

So, this shield prevents the chips inside, where the computing happens, being damaged by electromagnetic interference. And that’s the kind of thing that the phone itself gives up when you’re making calls, browsing the internet. Actually, that’s mostly happening during the power-up sequence. OK. So this is a main logic board. This is where everything happens. Behind these plastic bits of protection are the silicon chips. Now, it’s silicon dioxide, so, in many ways, it’s a lot like the material that comes in the screen. But, for the chips, that silicon dioxide has to be thousands of times purer. And so, in order to get that pure silica, instead of using sand from a beach they use this kind of material.

This is a quartzite. And this is so much purer, because heat and pressure has forced out a lot of those impurities during the process of its formation.

Did that start off as sand?

Yes. So, this would originally have been sandstone and, before that, sand, probably on a beach. And then it’s been metamorphosed into this quartzite. So this is really a metamorphic rock. Of course, we don’t actually really know where the silicon dioxide for the chips come from. It’s a little bit of a trade secret. But we’re pretty sure it’s stuff like that.

Also in the chips, safely buried underneath the plastic, are oxygen from the air, arsenic, phosphorus, gallium. And that all goes into making a semiconductor.

Holding the chips in, and a lot of these components, is solder. And that’s a bimetallic material. It’s usually made from a couple of metals. Traditionally, it’d be made out of tin. And tin comes from cassiterites, like this one from Cornwall, in the southwest of England. And again, traditionally, solder would usually have quite a lot of lead from things like this beautiful piece of galena. But because of some of the dangers of lead, a lot of technology, including actually this iPhone, now replace the lead with other metals, like silver.

 So, if we keep going down, the next thing we come to is the battery. And so this is packed full of lithium. And lithium is sourced from a couple of sources, at the moment, in the world. One of the main ones is lithium brine. And that’s basically just really salty water, a bit like this.

So, is that seawater?

This, once upon a time, would have been seawater, in a very ancient sea. But the lithium, along with a lot of other elements, get locked into evaporites, and then, at various points, have gone back into solution. One of the other sources for the lithium is pegmatites, like this beautiful sample here. Now, pegmatites are these wonderful igneous rocks produced deep within the earth’s crust. And you can see a lot of the minerals. And these are probably stuffed full of a lot of rare earth elements, lithium also one of them.

Now, if we go even further in, you can see things like this bit, here. This is the vibration unit. This is what makes your phone buzz in your pocket. And that’s stuffed full of rare earth elements – which actually aren’t that rare in the earth. But also things like neodymium, which makes the magnets. And again, many of those rare earth elements and the neodymium are likely sourced from things like this pegmatite.

So, what holds a lot of the components together and connects them up, and things like these contacts which connect one part of the phone to the other, they’re made of copper. Copper comes from rocks like this. This is a chalcopyrite. And you can see some of the beautiful minerals gleaming on this one. There’s also, in those contacts and in some of the wiring, other things like gold, silver, as well. And, in fact, some of the copper would originally have been produced and found as native copper. So, this is a piece of almost pure copper that would have been found in rocks, very early on.

And ‘native’ means?

‘Native’ just means it’s present as the metal itself, rather than as another mineral. And, holding all of these things together, and making up the case, is plastic. And, as we know, that’s oil. And here’s some now. So, crude oil like this is made up of the squished and heated bodies of billions and billions of microorganisms that lived millions of years ago.

So, as we’ve seen, there’s a lot of geology in a phone. And we’ll spend the rest of this week looking at some of the geological processes that go into forming the minerals that make up the technology you carry around in your pocket.