7 ms·

Scientists crack a 20-year nuclear mystery behind the creation of gold

87 points by prabal97 6mo ago

mcswell 6mo ago
I'm confused. The article is about how various excited states of tin are generated. But tin is atomic number 50, platinum and gold are 78 and 79 respectively. Can someone draw a line between these?
- bonzini 6mo ago
  It's about refining theoreticals models that are used to predict nucleosynthesis of heavier elements. The researchers used indium because we can obtain the required neutron-heavy isotopes for indium but not for heavier elements such as gold or platinum. But improving the model with data from indium, they say, makes it more accurate for gold as well? Why then gold in the title? Probably just because it's shiny.
  - adrian_b 6mo ago
    Platinum is also a peak of element abundance, together with its neighbor elements. So any model of how the elements have been produced must explain why the probability of making platinum and its neighbor elements, osmium, iridium and gold was higher than the probability of making other elements. The existence of other abundance peaks is easier to understand, e.g. the peaks at tin and at lead happened because these 2 metals have "magic" numbers of protons, i.e. 50 and 82, which correspond to complete nucleon layers. The peak at platinum is higher to understand, so to explain it you need accurate models. On Earth it is not obvious that the heavy platinum-group metals and gold are located on an abundance peak, because all these precious metals have gone deep inside the Earth, into its iron core, so the crust of the Earth is depleted in them, which has made them rare and precious. There are asteroids where the iron cores are easily accessible and they contain great amounts of platinum and related metals. However, the idea that mining that would be easy is extremely naive. On Earth, mining gold and platinum is easy, because they do not mix with silicate rocks so they can be found as native metals or sulfides/arsenides/tellurides that can be easily separated from silicate rocks and then the metals are easy to extract. On the other hand, in asteroids platinum and the other precious metals are dissolved in iron uniformly, so they are extremely diluted, in proportions of less than 1 part per million. Therefore, even if the total amount of platinum and gold is huge, concentrating one gram of platinum from one ton of iron would be tremendously difficult, requiring a huge amount of energy. Mining asteroids for the purpose of bringing something back to Earth will certainly not happen before solving much easier problems, e.g. growing back an amputated leg or any other part of the body. The fact that at least a startup exists that claims to work to achieve such mining is just a certain scam with no other goal than mine money from naive investors.
    - holoduke 6mo ago
      I thought the impact of Thea made heavier elements spread much more evenly towards the surface.
      - adrian_b 6mo ago
        True, but even with that, the amount of siderophile elements like platinum and gold in the crust is much less than in the core of the Earth ("siderophile" means that at the contact between molten iron and molten silicate rock such elements go into the molten iron). Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust.
        adolph 6mo ago
        > Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust. Wow, its wild to think of a counterfactual world without gold. Would those metals have emerged to the crust from volcanism or is that material not sourced deeply enough?
        adrian_b 6mo ago
        Volcanism at most brings material from the upper mantle, but usually such material becomes mixed with material from the crust, while ascending. The mantle has slightly bigger concentrations of precious metals than the crust, but the concentrations remain many times smaller than in the core. The reason is that both the mantle and the crust are made mostly of silicate rocks. The mantle is made of heavy silicate rocks and the crust is made of light silicate rocks, which float on the denser mantle. The metals that are resistant to oxidation do not mix well with silicates, so they tend to segregate from them, and then, being heavier than rocks, they tend to descend towards the core. If they reach the core, then they dissolve into the melted iron. When lava is expelled by volcanism, the precious metals contained in it usually separate from the silicates together with metal sulfides and arsenides, which makes them easier to find than if they were dispersed uniformly in the rocks. Other elements that ere much more abundant, for instance germanium and gallium, are harder to mine than the precious metals because they are not concentrated in distinct minerals but they are uniformly distributed in many rocks.
tcdent 6mo ago
And they said turning Lead into Gold was just heresy.
chasil 6mo ago
I am surprised that the s-process plays no role in the formation of gold.
luxuryballs 6mo ago
does anyone else experience an “eyes glazing over” effect when you read things like “Heavy elements such as gold and platinum are forged under extraordinary conditions, including when stars collapse, explode, or collide”? It seems totally beyond possible in scope and scale to validate something like this, even if you managed to get up close to one of these events it would still be too big and powerful to follow what is happening.
- kadoban 6mo ago
  It is quite difficult to validate if you only consider the most direct of means like smashing two stars together and then physically going out and picking up the pieces. There are other means to validate that type of thing though. Trying to come up with those means is a lot of fun. Can you think of any?
  - libertine 6mo ago
    I'm ignorant on the subject, but when you boil it down isn't this all about throwing things at each other?
    - vscode-rest 6mo ago
      [dead]
- vscode-rest 6mo ago
  [dead]
measurablefunc 6mo ago
Tangentially related from something I'm currently reading¹: > This is the reality of twenty-first-century resource exploitation: reducing vast quantities of rock into granules and chemically processing what remains. It is both awe inspiring and disturbing. One risk is that the cyanide and mercury used in the method could escape into the surrounding ecosystem. After all, while miners like Barrick insist they follow all the rules laid down by the US Environmental Protection Agency (EPA), campaigners warn that pollution often finds its way out of the mine. Indeed, a few years earlier the EPA had fined Barrick and another nearby miner $618,000 for failing to report the release of toxic chemicals including cyanide, lead and mercury. But the main thing I was struck by as I observed each stage in this process was just how far we will go these days to secure a tiny shred of shiny metal. > The scale, for one thing, was mind-boggling. As I looked down into the pit I could just about make out some trucks on the bottom, but only when they emerged at the top did I realise that they were bigger than three-storey buildings; the tyres alone were the size of a double-decker bus. How much earth do you have to remove to produce a gold bar? I asked my minders. They didn’t know, but they did know that in a single working day those trucks would shift rocks equivalent to the weight of the Empire State Building. ¹ Material World: A Substantial Story of Our Past and Future by Ed Conway
- prabal97 6mo ago
  > in a single working day those trucks would shift rocks equivalent to the weight of the Empire State Building. Oh. My. God.
SwuduSusuwu 6mo ago
[dead]
DanDeBugger 6mo ago
This is a goldmine, well, not literally. Still, I wonder if this could be a paradigm shift with other elements, and if so how many???
- thunderbong 6mo ago
  This isn't Reddit
  - DanDeBugger 6mo ago
    Yes, of course, this hadn't occurred to me. My apologies.

87 points by prabal97 6mo ago

I'm confused. The article is about how various excited states of tin are generated. But tin is atomic number 50, platinum and gold are 78 and 79 respectively. Can someone draw a line between these?

bonzini 6mo ago
It's about refining theoreticals models that are used to predict nucleosynthesis of heavier elements. The researchers used indium because we can obtain the required neutron-heavy isotopes for indium but not for heavier elements such as gold or platinum. But improving the model with data from indium, they say, makes it more accurate for gold as well? Why then gold in the title? Probably just because it's shiny.
- adrian_b 6mo ago
  Platinum is also a peak of element abundance, together with its neighbor elements. So any model of how the elements have been produced must explain why the probability of making platinum and its neighbor elements, osmium, iridium and gold was higher than the probability of making other elements. The existence of other abundance peaks is easier to understand, e.g. the peaks at tin and at lead happened because these 2 metals have "magic" numbers of protons, i.e. 50 and 82, which correspond to complete nucleon layers. The peak at platinum is higher to understand, so to explain it you need accurate models. On Earth it is not obvious that the heavy platinum-group metals and gold are located on an abundance peak, because all these precious metals have gone deep inside the Earth, into its iron core, so the crust of the Earth is depleted in them, which has made them rare and precious. There are asteroids where the iron cores are easily accessible and they contain great amounts of platinum and related metals. However, the idea that mining that would be easy is extremely naive. On Earth, mining gold and platinum is easy, because they do not mix with silicate rocks so they can be found as native metals or sulfides/arsenides/tellurides that can be easily separated from silicate rocks and then the metals are easy to extract. On the other hand, in asteroids platinum and the other precious metals are dissolved in iron uniformly, so they are extremely diluted, in proportions of less than 1 part per million. Therefore, even if the total amount of platinum and gold is huge, concentrating one gram of platinum from one ton of iron would be tremendously difficult, requiring a huge amount of energy. Mining asteroids for the purpose of bringing something back to Earth will certainly not happen before solving much easier problems, e.g. growing back an amputated leg or any other part of the body. The fact that at least a startup exists that claims to work to achieve such mining is just a certain scam with no other goal than mine money from naive investors.
  - holoduke 6mo ago
    I thought the impact of Thea made heavier elements spread much more evenly towards the surface.
    - adrian_b 6mo ago
      True, but even with that, the amount of siderophile elements like platinum and gold in the crust is much less than in the core of the Earth ("siderophile" means that at the contact between molten iron and molten silicate rock such elements go into the molten iron). Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust.
      - adolph 6mo ago
        > Without that impact, it is assumed that almost no platinum-group metals and gold would have remained in the crust. Wow, its wild to think of a counterfactual world without gold. Would those metals have emerged to the crust from volcanism or is that material not sourced deeply enough?
        adrian_b 6mo ago
        Volcanism at most brings material from the upper mantle, but usually such material becomes mixed with material from the crust, while ascending. The mantle has slightly bigger concentrations of precious metals than the crust, but the concentrations remain many times smaller than in the core. The reason is that both the mantle and the crust are made mostly of silicate rocks. The mantle is made of heavy silicate rocks and the crust is made of light silicate rocks, which float on the denser mantle. The metals that are resistant to oxidation do not mix well with silicates, so they tend to segregate from them, and then, being heavier than rocks, they tend to descend towards the core. If they reach the core, then they dissolve into the melted iron. When lava is expelled by volcanism, the precious metals contained in it usually separate from the silicates together with metal sulfides and arsenides, which makes them easier to find than if they were dispersed uniformly in the rocks. Other elements that ere much more abundant, for instance germanium and gallium, are harder to mine than the precious metals because they are not concentrated in distinct minerals but they are uniformly distributed in many rocks.

tcdent 6mo ago

And they said turning Lead into Gold was just heresy.

chasil 6mo ago

I am surprised that the s-process plays no role in the formation of gold.

luxuryballs 6mo ago

does anyone else experience an “eyes glazing over” effect when you read things like “Heavy elements such as gold and platinum are forged under extraordinary conditions, including when stars collapse, explode, or collide”? It seems totally beyond possible in scope and scale to validate something like this, even if you managed to get up close to one of these events it would still be too big and powerful to follow what is happening.

kadoban 6mo ago
It is quite difficult to validate if you only consider the most direct of means like smashing two stars together and then physically going out and picking up the pieces. There are other means to validate that type of thing though. Trying to come up with those means is a lot of fun. Can you think of any?
- libertine 6mo ago
  I'm ignorant on the subject, but when you boil it down isn't this all about throwing things at each other?
  - vscode-rest 6mo ago
    [dead]
vscode-rest 6mo ago
[dead]

measurablefunc 6mo ago

Tangentially related from something I'm currently reading¹: > This is the reality of twenty-first-century resource exploitation: reducing vast quantities of rock into granules and chemically processing what remains. It is both awe inspiring and disturbing. One risk is that the cyanide and mercury used in the method could escape into the surrounding ecosystem. After all, while miners like Barrick insist they follow all the rules laid down by the US Environmental Protection Agency (EPA), campaigners warn that pollution often finds its way out of the mine. Indeed, a few years earlier the EPA had fined Barrick and another nearby miner $618,000 for failing to report the release of toxic chemicals including cyanide, lead and mercury. But the main thing I was struck by as I observed each stage in this process was just how far we will go these days to secure a tiny shred of shiny metal. > The scale, for one thing, was mind-boggling. As I looked down into the pit I could just about make out some trucks on the bottom, but only when they emerged at the top did I realise that they were bigger than three-storey buildings; the tyres alone were the size of a double-decker bus. How much earth do you have to remove to produce a gold bar? I asked my minders. They didn’t know, but they did know that in a single working day those trucks would shift rocks equivalent to the weight of the Empire State Building. ¹ Material World: A Substantial Story of Our Past and Future by Ed Conway

prabal97 6mo ago
> in a single working day those trucks would shift rocks equivalent to the weight of the Empire State Building. Oh. My. God.

SwuduSusuwu 6mo ago

[dead]

DanDeBugger 6mo ago

This is a goldmine, well, not literally. Still, I wonder if this could be a paradigm shift with other elements, and if so how many???

thunderbong 6mo ago
This isn't Reddit
- DanDeBugger 6mo ago
  Yes, of course, this hadn't occurred to me. My apologies.