Mining for Gold (GOLD!)

This BBC podcast is supported by ads outside the UK. It's time to see what you can accomplish with Shopify by your side. Acer does it. So, we can now listen to your podcast. Struggling with what to buy you for Christmas. Because you hate diamonds. I hate diamonds. Was that ever on the list? No, but it's nice to have a clear no. I want a diamond crown. Yeah, and I know I can't give you the diamond crown, so I'm just going to have to get you a book token instead. But are you the same with other precious metals? No, no. Gold, for example. Gold. I'm in love with gold. Gold is a special place in my heart. Okay, fine. And not just because of Spandau Ballet. Yeah, because we're obviously going to talk about gold, right? But it's very difficult to talk about gold when everyone thinks that. Every time you say gold, you have to go, gold! The second time, like the ass guy. I'll tell you what. What? We'll limit ourselves. Yeah. You're allowed to say gold three times. Really? Three times in this entire episode. And you've already used two. Oh, that's so dope. When do I do the last one? It'll be right at the very end, of course. Because we'll be talking to scientists and stuff. It'll feel really childish. You never know. But do you think in their professional life that they're also all going? Okay, Chemistry 101. Welcome today. we'll be talking about gold and they're going, gold! Every time. I like to think so. I like to think that scientists are just as childish and incapable of passing off on an opportunity to sing Spandau Valley than the rest of us. We got a question in about gold this week from listener Bernie who got in touch by emailing curiouscases at bbc.co.uk with this question. Hello, I'm Bernie from Whitley Bay. I've read that all the gold that's ever been mined would fit in an Olympic swimming pool but then I think about the gold in my house our wedding rings there's gold in our mobile phones and computers and audio equipment and sometimes in our teeth and then I think about the other people in our street and all our ancestors and I think about the gold in industrial applications all over the world isn't the Olympic swimming pool a bit on the small side for all that gold the thing is it's probably not the first tooth that it's been in you know probably your Ancestor's tooth and your tooth are probably the same thing. That's, yes, I know there's a lot of circulation of gold. We will get to that. But you don't want to feel, this has served many people. Then they died and we ripped it out of their head. We melted it again. It's going into you. And it's happened so often. This is not the first steak that this has tasted. This is not the first apple it has chewed. Lovely. Pleasant. Well, luckily, today in the studio, we have got some people to help answer these questions. Graham Hutchins, Regis Professor of Chemistry at the University of Cardiff, and Francis Wall, who is a professor of applied mineralogy in the Cambon School of Mines at the University of Exeter. Well, let's start with a little appreciation of gold. Graham, what is it about gold? What are the superpowers of gold that make it so popular? It's just so beautiful and everybody likes it because it's beautiful. But it's also got some fantastic properties. It's malleable, it's ductile, it's extremely conducting and so it's useful. It is to me remarkable that it's a thing that was treasured in the earliest of societies. And now we've discovered so much more to it, so much more depth to its usefulness. Yes, I mean, basically in historical times, you can go back to about 40,000 BC and you will find bits of gold in caves that were inhabited by, no one had been inhabited by humans in Spain. Archaeologically, it's always been in sort of death masks and jewelry that's associated with royalty and things like this. And it's only in the last probably century that we find really different uses for it. But in its bulk state, when you have a sort of... I've got a wedding ring on here. It doesn't tarnish, it doesn't react with the air. It's a very unreactive material. So if you've got some gold and the house catches fire, the gold's there afterwards. OK? If you've got money, it's not there. Yeah. Silver wouldn't be there because it will oxidise. But gold doesn't. It's like the cockroach of the periodic table. Yeah. I've never thought of it that way, but it's quite good. And why? Chemically? Chemically, what's going on there? So it's because of its electropositivity. It wants to hang on to its electrons. It wants to be a metal. So it doesn't want to share, it doesn't want to think, so it won't react with it. No. Whereas silver is quite happy to share its electrons and it oxidises in air. So, you know, if you've got any silver, you have to clean it, don't you? Well, you should clean it. Yeah. I'm not there every week. No, no, no. There's just so much of it down there. Honestly, I've got teams of people. This happens in nature as well, of course, because gold you find as, we call it native gold, the native element. Silver, you can find, is native, but you get more of it in other minerals. And copper is combined with sulfur. So you're always mining copper sulfides. And although you can occasionally find copper as the metal, that's quite a special find if you find that in nature. So you're going down the periodic table group, then they're becoming more and more antisocial, if you like, down to gold, where it likes to sit on its own and not make more complicated minerals. The antisocial cockroach. I mean, we may be anthropomorphised. The worse I can make it sound, the more gold for me. Yeah, fair enough. And where does it come from? Well, where it originally comes from is extraterrestrial. It's the original ET of the periodic table. But you'll know more about that. Yes, but I know. It's supernovas. Yes, yes. And neutron stars. Collisionary neutron stars. You know, even though I've said this story, and I've talked about this on a million shows about how we're all made of things that explode in stars. I still find the whole process unbelievable that a star explodes, spreads it over a huge amount of distance. Then somehow this is all gathered together. And also it manages to clump in findable amounts. So you have the solar system material coalescing. And then, of course, the planets the size of the Earth differentiated. So we have the metallic core and gold is metallic. So there probably more gold in the core that we absolutely cannot get at But luckily for us some of it did end up in the crust in parts per billion so tiny amounts And then how does it get to amounts that we are interested in and could actually think about mining? Then it's moved around by natural solutions that are maybe acidic enough to dissolve it up and move the gold from one place to another. And that's in particular geological environments, might be beneath a volcano or where plates are colliding and you have a lot of heat and pressure and fluids moving around. And once they've picked the gold up, eventually it will become insoluble again and deposit. And if you're clever enough to understand that process, you know where to go and explore for gold. So they would have found each other, these molecules of gold would have found each other when it was all liquefied. So they're sitting at different levels. Yeah, maybe when it was moving around. Moving around. They'd have clumped then and then over there's cool down to being nuggets of gold. But a lot of gold that's mined these days is actually in tiny amounts. So it's not in nuggets that you would see. You can't see it in the rock at all. You have to go and analyse it to find out that there's really gold there. Because if you have one part in a million parts of the rock, that's actually quite a good gold economic deposit these days. Really? They've got one part gold and whatever it is, 999,999 parts of rock. That's enough for you to extract that? Yes. Wow. By a process of what? So if that's your original rock, then it would be mined either by making an open cast mine, a quarry. A lot of large scale mines are done like that now. Or by going deep underground. Gold is valuable enough that the deepest mines in the world, four kilometres down, are gold mines in South Africa. And they went three kilometres down in India. Then you bring it up to the surface and then you have to crush all the rock up, which is very energy intensive. And then nowadays they put it in big tanks with probably a cyanide chemical. And the cyanide will combine with the gold and take that out. And then you precipitate that out with carbon or something. and then that goes away to the refinery. But what did you say? One in a billion? In the Earth's crust, it's one in a billion is how much gold there is. But if it's concentrated to one in a million, then it may well be possible to mine. What's the ratio in mobile phones? Because there's some in there, isn't there? Can I not just crush up some mobile phones? Oh, yeah, you could. A mobile phone is a better ore deposit than some of the stuff that's mined. And that is one of the main drivers of recycling any electronics. It's the value of the gold. So poor old metals like tin, like Cinderella metals, really super important. But it's much harder to get those recycled. Whereas when something has gold in it, then it's much more likely that people will go and get that tiny bit of gold. If you went to Johannesburg in the 1980s, the whole city was surrounded by mine dumps. And one of those had a drive-in movie place on the top of it. And so if the movie was bad, you could actually just watch the city lights of Johannesburg. and often the movies were quite bad. But they're not there anymore. They've all been reprocessed. So this was presumably slag, was it? Was it runoff from mines? It was what they couldn't process 50 years ago. But now the chemical processors are far better. So it was worth their while to dig it all back and reprocess it. Clean it all up. So where do they put the stuff that was a runoff from that? Where has that gone? That's probably gone into making roads and barriers. Right, OK, there's not another... There's not another thriving cinema across. No, this is a really important point, though, because people often say, let's go and rework mine waste, whether it's for gold or critical minerals or something. But if you imagine your mine waste has got one part per million, if you've taken that out, you've still basically got the whole lot to go somewhere else. So you're not solving your problem of the mine waste unless you can actually do something useful with it, like make it into road aggregate or redefine your hills so they're not just ugly waste hills. They're actually useful things for people to do agriculture or maybe you can make a ski slope or something. Do we know how much has been mined in total across all of human history? Yeah, the World Gold Council keeps a tally of this and it's 216,265 tonnes at the end of 2024. That would be metric tonnes. So gold, far, far more than any other metal, has been kept in circulation. Now, if you can trust, I think gold throughout all history has been valued so much that it's been kept and probably passed on through the generations. And now it would be sometimes recycled through a smelter and so on and go on into next uses. Whereas if you look at something like tin, for example, which has been used in the bronze from the Bronze Age and in tin cans and all the uses now in electronics, most of that has turned up in a rubbish dump somewhere wasted. whereas gold of course we've looked after very carefully so it's a great lesson for what we should be doing with all metals in the future. Yeah because there is an appealing sense with gold that this was once a pharaoh's adornment it got stolen from whatever the grave was then it ended up somewhere else on the roof of a church in Mexico it got stolen off the roof of a church in Mexico but the same it is the same gold that is going to and then somebody's mouth and their teeth but historically its path has been very much that this has been used again and again and again. Great. Starting a business can be overwhelming. You're juggling multiple roles, designer, marketer, logistics manager, all while bringing your vision to life. Shopify helps millions of business sell online. Build fast with templates and AI descriptions and photos, inventory and shipping. Sign up for your one euro per month trial and start selling today at shopify.nl. That's shopify.nl. It's time to see what you can accomplish with Shopify by your side. So, we can now listen to your podcast. electrical circuits and because it's so dense you don't need that much of it to do these things but the more recent use of gold is in the field of catalysis catalyst is a material that makes reactions go faster it's the simplest definition and gold when you divide it down to just a few atoms or a nanoparticle becomes extremely reactive so it's totally different from the bulk state with the jewelry and everything. Now it will react with oxygen and it will do interesting chemistry. Is this the work that you were doing in the 80s? Yes I mean basically I was working in industry and I was asked to come up with a new catalyst for a process that was taking acetylene and hydrogen chloride and making vinyl chloride So vinyl chloride is an important monomer for making polyvinyl chloride PVC So I think most people know what PVC is. That's quite a big deal in the 80s. Yes, excellent clothes and shoes, etc. But the catalyst that they were using was a mercury catalyst. And it's a really nasty material. material. Mercury's teratogen, it causes birth defects. And the process that it's used in, it's operated at 200 degrees, but the mercury catalyst goes into the gas phase at about 180 degrees. And so the mercury is swept out of the reactor and ends up in the environment. So every year, until very recently, around 1,000 tons of mercury. 1,000 tons? Yeah, of mercury was being released into the environment around these plants. And the idea is that using gold instead eradicates the need for that at the end of the process. I mean, I was asked to find a new catalyst and it was a scientific paper. That gave me the idea because this person had done all the experiments and correlated all these catalytic materials and came up with a graph that showed no correlation whatsoever. And I looked at it and replotted the data in a different way. And I said, if that's right, then gold will be the best catalyst for the reaction. And it is. And it turned out to be. Yeah. So that's a eureka moment, I think, is what people say about that sort of thing. I mean, that was a big breakthrough moment with gold. But the thing is, is that there's been other areas where gold has also provided a similar breakthrough. I mean, medicine, for example. Yeah, I think it all comes down to how can you make gold nanoparticles, because medicine revolves around, you know, sort of nanoparticles of gold 5, 10 nanometers in size, so they're still very small. And if you put the gold into a particular tissue in cancer treatment, for example, it interacts very well with radiation and amplifies the effect of the radiation. And so it can destroy the cancer tissue without destroying the healthy tissue around it. Sorry, how on earth do you put gold into cells? Well, there's various ways you can do it. I mean, there was an experiment that was done in 1980 where somebody fed a bacterium with gold solution and the bacterium made gold nanoparticles spontaneously because it didn't want the gold. So it makes the gold nanoparticles. It pooped out gold. Yeah, basically. Different meaning for nugget. Yes, yes, it's a different meaning. And so a lot of people view that as a way of making gold nanoparticles. But there's work that's been going on in Texas where for pancreatic cancer, they're injecting the tumour with a gold solution and the tumour makes gold nanoparticles, which then they can treat with radiation because it's targeted into that organ. Absolutely extraordinary. I mean, see why I love this stuff? No, it's astonishing. But my question is very much more mundane than that. Why is it on all my headphone jacks or sound jacks in high-end home sound systems, the end of them are all gold? Well, because it's such a good conductor. And do I hear less crackle? Do I hear more fidelity? Yeah, it transports the electrons far more efficiently than any other metal will do. Tell you who else likes gold in their electronics other than just fancy DJs, astronauts. Because it's so reliable, it can be used in the harshest environments possible. So we've got a special guest joining us now to explain his top uses of gold in outer space. Hello, I'm Tim Peake. I'm a British astronaut who flew to the space station in 2015 for six months. Gold is an amazing element. And when I speak to most kids about gold, they say, well, it's shiny. And that's very true. and shiny is why it's good for space because shiny kind of explains some of its qualities like very reflective and it's shiny because it doesn't react with oxygen doesn't react with water very easily so it's a noble metal it's chemically inert got a fairly high melting point so all of its sort of chemical properties make it good in that really harsh difficult environment of space so in at At number three, we have use on rovers like our Martian rovers and even the lunar modules. Now, because gold is very reflective and it's not corrosive and it doesn't tarnish, it can be used on our spacecraft. One interesting fact is if you go to the Science Museum in London and you look at the Apollo 10 command module that they've got there, it's actually right next to my Soyuz capsule, you might be able to spot two little gold domes on the command module. Now, these gold domes are actually the urine outlet for the command module. So when the astronauts needed to go for a wee, they would put on this kind of latex cuff, they'd pee into it, they'd put it into the tube and the tube would flush it through out into space. And the little domes are coated in gold. And the reason that, again, is because it's a very unreactive metal. And it was also able to electrically isolate it from the rest of the components inside that command module as well. In at number two, we've got thermal insulation, radiation shields and mirrors because gold is a reflective metal. In fact, not only is it reflective in the visible spectrum, so we can see ourselves in gold if we look into it, it's actually very, very reflective in the infrared spectrum. About 99% of all IR is reflected by gold. So if you have something like the James Webb Space Telescope, the mirrors it uses to focus all of that IR energy are their gold. We have gold in thermal insulation because it reflects that heat away. So gold mylar can be used to coat the outside components. That was used on the lunar module as well, keeping whatever it is inside protected from any potential harmful effects from radiation. And finally, number one, gold can be used on astronauts' helmets because it's reflective, but it's also valuable. malleable. So when it's thinly coated, we can cover our visors in gold and that protects us from the harmful rays of the sun. But it's a very thin layer so we can actually see through it and still do our job. And a little unknown fact is when I was on my spacewalk, the first time we went into night, we get a little warning or we get told to raise our visors and put our glove heaters on. And as we went into the shade, we're going from about 120 Celsius in the sunlight to about minus 150 in the shade. So it's a very rapid cooling process. And I probably wasn't quick enough raising my gold visor. It was still down. And I heard this cracking noise. And for a horrible few moments, I thought, my visor is cracking. This is not a good time to be on the spacewalk. And actually what it was, it was that rapid cooling. and the gold metal around the bizer was shrinking so much. It was just causing some of the other components to shrink and give that kind of cracking sound as well. But certainly got my attention for a few moments. So thank you for letting me share some of my stories about gold and why we use it in space. And a very happy Christmas to Hannah, to Dara, and to all of you curios out there. That pretty thorough He answered that one really solid I mean really has covered all the angles on that Can I ask a, it might be a very stupid question. Is there any use of gold that you find slightly irritating? Irritating? Specifically, edible, you know, people who are putting gold leaf onto really expensive burgers. I was going to mention that, yes. You see these expensive drinks where there's gold leaf floating in them. basically it will go into the stomach it will just pass through it's totally useless yeah but it's free for someone to pan many years later does it even have been many years water authorities should be mining it they could recover it, the sewage works should we go back to our listeners' question? I think we should Bernie's original question that started all this was have we only mined the volume of an Olympic pool? now there's been a huge debate about Olympic pools because how deep is an Olympic pool? The deeper you make in the Olympic pool, the less turbulence, the faster the swings. There's been a kind of a race literally to the bottom in a swimming pool to make them as deep as possible. So you're saying basically any number that I come up with, you can say, just make the Olympic pool deeper. Yeah, just keep shelling out of the... And then we'll get faster swimming. It's win-win. And more gold on the whole thing. Plus swimming and the fact will remain true. We're going for a two metre depth. OK, OK. That is the depth at which most people go, oh, a little bit too deep. So that's the two metres. OK, all right. So we said from the Gold Council, we said 216,000 metric tons. Gold, as you mentioned, super dense. So it's roughly 19,000 kilograms per cubic meter, which is heavy. That's heavy. Okay. So we get in total then the volume of all the gold we've got is, this is just me shouting numbers on the radio now, isn't it? Yeah, it is. It's 11,180 metres cubed. That's what I'm working at. Olympic pool, 2,500 metres cubed. Really? That's going on your standard 50 metres long, 25 metres wide and two metres deep. Two metres deep. So unless you quadruple the depth of your Olympic swimming pool, I think the total amount that we've got is about four and a half Olympic swimming pools. So basically we're saying Bernie's pool fact is wrong. But it's one of these facts that's been said, because I've heard that a lot, that it's been one of these things that gets mentioned a lot the Olympic swimming pool is this is the amount of gold we have there was a point not that long ago that that was true oh really? yeah because if you actually go historically through it the amount of gold we have we just intensified our mining over the last century century and a half basically from about the 1950s upwards so really at some point between say 1900 and 1950 we hit the swimming pool I'll be honest with you I think if you go back to his question where he's saying you know you're sitting in your house, you can see this bit of gold here, this bit of gold there. When you consider all of that, James Webb telescope, one of the blingiest things ever made by humans, like actually four and a half swimming pools still isn't very much. Isn't very much, no. I can picture that. And yet somehow that is every heirloom, every wedding ring, going back to every Mexican church, and every Egyptian tomb, all of that. Yeah. And presumably part of that is because you can spread it out incredibly thinly. One gram of gold can be hammered out into a two kilometre long wire. Oh my God. Right? That is right. And if you think about, you know, those gold chains that you get, even like the fancy expensive ones that are like largely made of actual gold. I mean, that's just a little bit of wire. It's probably nothing, isn't it? Now you're ruining gold. You've ruined diamonds in the past and now you've ruined gold. What, hang on, this selfish cockroach? What are you talking about? And obviously, the fact that you can melt it down easily kills any issues of provenance. You know, gold just has a value. No matter what it was when it got stolen, it can be melted down. Well, that's it, the Louvre. The Louvre. When's that going to appear in the house? It disappears very quickly, but you can, there's lots of schemes that will track gold. So you can buy fair trade gold in jewellery. You can buy from small-scale miners, in the forests in South America. Then there's all that what comes through a smelter is an interesting problem. Sometimes you can track natural gold by looking at the trace elements in its composition. And if you imagine a smelter that's taking all kinds of things, I think that's actually harder to know what's legitimate and what might have just been stolen from the Louvre. I think that's a more difficult question. The famous robbery, the Brinksmart robbery, where there was an enormous amount of gold that was stolen. Because the impurities in that Brinksmack gold, it was known to the company. It was Johnson Matty gold. They know that they've re-smelted some of that because it's come back to them. So that's been going around. So only half of the gold was recovered. So they say only half of it was recovered. Does that mean that they feel the rest has already passed, has already been... It's been reused. It's been reused. You've been drinking it in your fancy cocktail. Yes, every chance. That's the Gold Leaf Burger was in Heathrow at one stage, which is not how they sell it. Quite well, it is. Yeah. An absolute pleasure. Thank you so much for coming in. Thanks for our guest today. Graeme Hutchings, Francis Wall and of course, all the way from space, Tim Peake. See? Much better than diamonds. Yeah, it is, isn't it? Because diamonds don't do like cool things. No. I mean, they sort of did some cool things. But listen back to that episode if you want to hear more about that. Yeah, yeah, yeah. But I just love the way the fact that we fixed on this thing and really went for it in a big way in the ancient world. In a number of different cultures, when this is the thing. Yeah, top of the pyramids. Oh, absolutely. Aztecs, you know, unrelatedly, people really went for it in a big way. I mean, all the way through history. The Greeks, the Trump administration. I mean, across the millennia. People of Barrow have loved this thing. And then we find it just really interesting if you really want to hear high quality music or whatever, or for your mobile phone. It just remains this very useful thing. Yeah, we'll take pictures in space. It's lovely, isn't it? Do you reckon if aliens come across the James Webb telescope, they'll be like, I see they've harnessed the chemical properties and electrical conductivity. No, they'll go, this person, James Webb, must have been a great king that he's buried in space with his gold crown. Let's go and nick it. Yeah. Precisely what they'll do. We're going to go back and go, where the picture stopped? And they're assuming we've stripped it for parts. Oh, that's the thing about gold. Gold! I won in the chamber. That's Shopify.nl. It's time to see what you can accomplish with Shopify by your side. 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