> Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg/kg gold), hot, water ± carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry.
I don't have access to the full paper but if they tested anywhere near those concentrations, it definitely won't apply to seawater. The amount of gold in oceans is estimated at 1 gram of dissolved gold per 100 million liters of seawater. The hydrothermal fluids that precipitate out gold in orogenic deposits are closer to 100,000 kg per 100 million liters.
This whole experiment is kind of nonsense. Orogenic gold deposits form under high pressures when tectonic plates collide, creating deep faults and shear zones and causign tons of hydrothermal fluid (at 200-450C) to penetrate those new cracks and dissolve the gold contained in them before carrying it all upwards. The chance that piezoelectricity plays much of an effect in those conditions is almost nil.
basically, yes, but the voltage required is very low (what needs to be large is the current), and you need to get the gold to dissolve. https://www.sciencedirect.com/science/article/abs/pii/S08926... is one of an enormous number of papers on the process, and ipmi has a careers video on youtube: https://www.youtube.com/watch?v=hAkWMdrLXmo. shandong xinhai mining equipment corporation has a bunch of youtube videos marketing their equipment for this purpose to gold mine owners
i haven't tried, but as i understand it, gold is one of the easiest metals to reduce; even trivalent gold is at +1.52 volts above the she: https://en.wikipedia.org/wiki/Standard_electrode_potential_(..., and monovalent gold is the noblest of all metals at +1.83 volts. that table doesn't have another reduction to metallic state until platinum at +1.188 volts, then palladium at +0.915 volts, silver at +0.7996 volts, mercury at +0.7973 volts, trivalent thallium at +0.741 volts, etc. the commonplace metals are far away from this: univalent copper is at +0.52 volts, the more usual divalent copper at +0.337 volts, trivalent iron at -0.04 volts, divalent lead at -0.126 volts, tin at -0.13 volts, nickel at -0.257 volts, cadmium at -0.4 volts, divalent iron at -0.44 volts, zinc at -0.7618 volts, etc.
in water you can't really electrodeposit metals that are much more negative than zinc because at -0.8277 volts† you start reducing hydrogen from the water instead of reducing the dissolved metal. so things like silicon (-0.909 volts from quartz), vanadium (-1.13 volts) and titanium (-1.37 volts from trivalent titanium ions) are out of reach. by contrast, the difficulty with gold is that you can't keep it from depositing—so you can't get it into solution in the first place
voltages like 0.8 volts may not sound like much, but that's because we're used to currents that are, compared to the number of free electrons in the metal, unbelievably small. 0.8 volts is enough to rip apart a piece of metal atom by atom. consider a mole of zinc anodically dissolving; every atom loses two electrons. avogadro's number of electrons is about 96485 coulombs, about 26.8 amp hours. so, if your other electrode is the she, anodically dissolving a mole of zinc (65.39 grams) yields 2 · 96485 coulombs · 0.7618 volts = 147 kilojoules, which works out to about 2.2 megajoules per kilogram. that's a substantial amount of energy
because of gold's extreme nobility people usually complex it with cyanide or thiourea in order to do things like electroplating. its standard electrode potential to go to metallic state from the dicyanide complex is only -0.6 volts. but i don't know what form it's in in the oceans
______
† these potentials are all under standard conditions: unit activity for every reagent, 25° temperature, one atmosphere, etc. things like acidity and temperature can shift them a bit; https://en.wikipedia.org/wiki/Pourbaix_diagram is all about how they change with acidity, for example. but i don't think there exist conditions extreme enough to electrowin metallic vanadium or titanium
No, closer to alchemy is the actual creation of gold from other elements with nuclear physics.
Was demonstrated quite a long time ago, but is not really practical to get meaningful quantities out of it.
(That is why I always prefered physics over chemistry - my chemistry book in school started with the story of the alchimists and concluded that they were bound to fail as gold cannot be created.
And in my physics book was just the formula to create gold)
> No, closer to alchemy is the actual creation of gold from other elements with nuclear physics.
The place where this happens is in the liquid mercury target of the Spallation Neutron Source at Oak Ridge. Here, high energy protons shatter (spall) mercury nuclei, producing fragments that can include gold. An uncommon isotope of mercury can also be converted to gold by neutron capture.
> is not really practical to get meaningful quantities out of it.
you can build the entire neutron spallation reactor out of materials much cheaper than gold, and you can get unlimited quantities; the only impracticality is that the humans are still really bad at building machinery
> not really practical to get meaningful quantities out of it.
It is quite practical. You just pour a big pile of hydrogen out, let gravity compress it until it starts fusing. Initially it will only create helium but near the end of the pile’s life you will get mountains of the other elements too.
Easy breasy. It just takes time and quite a bit of space and hydrogen. Much harder to scale it down of course. But think big and aim for a star as they say.
‘Natural’ fusion will only get you as far as iron. Supernovae may produce heavier elements, but the heaviest elements like gold are probably produced in neutron star collisions.
Supernova explosions are good enough to make gold (and most other heavier elements until plutonium) by neutron capture.
Fusion, as you say, produces quantities that diminish very quickly for the elements beyond iron (iron 56 has the greatest binding energy of any nucleus and the binding energy decreases slowly after it), so that the last element that is produced in non-negligible quantities by fusion is likely to be germanium.
Not really I think, as this is not transforming something else into gold, it just kind of lumps existing gold together (if I understood the article correctly).
We have a name for that kind of alchemy - nuclear fission/fusion.
Because gold is so inert (a noble metal) its counterintuitive to see it in other forms eg in solution. In that sense manipulating gold in other forms than its elemental form probably feels like alchemy in common parlance.
I know aqua regia is relatively normal but I still find it weird to think of gold being dissolved
Gold is difficult to oxidize, but once oxidized it has some of the biggest ions, which stay easily in solution if no reducing agent is present.
The ion Au(I) has about the same size as the ions of potassium (which are exceeded in size only by cesium, rubidium, thallium and radium).
The ion Au(III) has a more normal size, but it is still relatively big, similar to the trivalent ions of the rare earths.
The big size of the gold ions is one of the reasons why its combinations with small ions, like oxide and sulfide, are unstable, so you cannot find such minerals in nature.
On the other hand, the gold ions form stable compounds with bigger ions, like telluride. Therefore there are many minerals where gold is combined with tellurium (unlike silver and copper, which combine with the smaller sulfur).
Nevertheless, on Earth tellurium has an abundance almost as low as gold, even if tellurium is abundant in the Solar System. The reason is that tellurium is easily vaporized, so less of it has condensed when the Earth has formed and a good part from what has condensed initially has been lost later, when the Earth has been heated by many asteroid impacts during its early history.
While tellurium is rare because it went up, being lost as vapors, gold is rare because it went down and most of it is dissolved in the iron core of the Earth. Because both tellurium and gold are very rare at the surface of the Earth, the chances of them meeting together in amounts great enough to form a mineral are very low.
The result of this scarcity of tellurium on Earth is that most of the gold can be found as native gold and only a smaller fraction is found in compounds with tellurium. Had tellurium not been lost from Earth, the amount of native gold would have been very small, similarly with the much smaller amounts of native silver and copper that exist versus the amounts available in sulfide minerals.
Thanks for sharing this - excellent content. I've been out of the game for a long time now but isn't this just the case that Gold is too soft as an ion to mix well with stuff like oxides?
Cs(I) should be larger than Au(I) but it seems to form a comparatively stable oxide Cs2O. But yes Tellurium is also a nice soft element so AuTl have a good affinity for one another.
Was unaware of their chemistry, it doesn't even ring a bell tbh I wonder if I had ever encountered it before. I did enjoy studying the Post Transition Group Metals back in the day
Yes, as I have said, size is only one of the reasons of incompatibility with oxide ions.
As you say, gold has a much higher electronegativity than cesium and rubidium, i.e. not much lower than that of silicon, which makes it a "soft" ion, and that reduces the stability of any compound with oxide or hydroxide or fluoride ions. On the other hand, the incompatibility with the "softer" sulfide is mostly caused by the size ratio.
Well I'd argue getting threatened with a knife is relatively normal in London but that's off topic :)
Aqua regia is not particularly exotic as compared with all the fancy ways you can harm yourself or react things in Chemistry. You can probably prepare it at home using stuff that might be buyable over the counter.
Getting your hands on things like azides or Polonium 210 or having access to a nuclear reactor to do ad hoc fission/fusion is a lot less normal on that scale.
Additionally aqua regia has been known for quite a long time, from before we even knew about gases
Fwiw I forgot what the magic cleans everything mix was but I want to say it was H2SO4 and cif which we'd just squirt around in our fume hoods
For sure!
Cleaning solution, you’re thinking Piranha solution probably.
Aqua Regia definitely isn’t exotic (same as getting threatened with a knife), but also isn’t going to be nice to be around, and getting ‘cut’ is pretty easy if you don’t pay attention.
And either one are frowned upon at most dinner parties. At least the ones I’ve been to, but I try not to judge ;)
Obviously my comment was meant in jest, but I still think your typical 17th century alchemist would be quite convinced you've figured out Chrysopoeia if you showed them this process—even if it's just lumping trace amounts of gold together.
Fred Hoyle wrote a pop sci book in the sixties talking about how things worked in early earth formation with prosaic imagery of gold squeezing around in quartz.
What's stopping someone from deploying this in the ocean water to capture gold?
Quartz crystal array + electricity -> gold layers?
1 You have to squish the quartz that cist money unless you put the crystalsbetween two tectonic plates.
2 The concentration of disolved gold is lower in seawater than in hot hydrothermal mud.
3 Perhaps with realistic values, this is very low and even in ideal conditions ypu need a few thousands years to get a visible chunk of gold.
From the abstract [1]:
> Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg/kg gold), hot, water ± carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry.
I don't have access to the full paper but if they tested anywhere near those concentrations, it definitely won't apply to seawater. The amount of gold in oceans is estimated at 1 gram of dissolved gold per 100 million liters of seawater. The hydrothermal fluids that precipitate out gold in orogenic deposits are closer to 100,000 kg per 100 million liters.
This whole experiment is kind of nonsense. Orogenic gold deposits form under high pressures when tectonic plates collide, creating deep faults and shear zones and causign tons of hydrothermal fluid (at 200-450C) to penetrate those new cracks and dissolve the gold contained in them before carrying it all upwards. The chance that piezoelectricity plays much of an effect in those conditions is almost nil.
[1] https://www.nature.com/articles/s41561-024-01514-1
So, in absence of quartz we could put large voltage sources on rocks and get gold out?
basically, yes, but the voltage required is very low (what needs to be large is the current), and you need to get the gold to dissolve. https://www.sciencedirect.com/science/article/abs/pii/S08926... is one of an enormous number of papers on the process, and ipmi has a careers video on youtube: https://www.youtube.com/watch?v=hAkWMdrLXmo. shandong xinhai mining equipment corporation has a bunch of youtube videos marketing their equipment for this purpose to gold mine owners
Ocean water contains dissolved gold, although I wonder if the other elements in sea water would attach to the quartz or rock electrode first.
i haven't tried, but as i understand it, gold is one of the easiest metals to reduce; even trivalent gold is at +1.52 volts above the she: https://en.wikipedia.org/wiki/Standard_electrode_potential_(..., and monovalent gold is the noblest of all metals at +1.83 volts. that table doesn't have another reduction to metallic state until platinum at +1.188 volts, then palladium at +0.915 volts, silver at +0.7996 volts, mercury at +0.7973 volts, trivalent thallium at +0.741 volts, etc. the commonplace metals are far away from this: univalent copper is at +0.52 volts, the more usual divalent copper at +0.337 volts, trivalent iron at -0.04 volts, divalent lead at -0.126 volts, tin at -0.13 volts, nickel at -0.257 volts, cadmium at -0.4 volts, divalent iron at -0.44 volts, zinc at -0.7618 volts, etc.
in water you can't really electrodeposit metals that are much more negative than zinc because at -0.8277 volts† you start reducing hydrogen from the water instead of reducing the dissolved metal. so things like silicon (-0.909 volts from quartz), vanadium (-1.13 volts) and titanium (-1.37 volts from trivalent titanium ions) are out of reach. by contrast, the difficulty with gold is that you can't keep it from depositing—so you can't get it into solution in the first place
voltages like 0.8 volts may not sound like much, but that's because we're used to currents that are, compared to the number of free electrons in the metal, unbelievably small. 0.8 volts is enough to rip apart a piece of metal atom by atom. consider a mole of zinc anodically dissolving; every atom loses two electrons. avogadro's number of electrons is about 96485 coulombs, about 26.8 amp hours. so, if your other electrode is the she, anodically dissolving a mole of zinc (65.39 grams) yields 2 · 96485 coulombs · 0.7618 volts = 147 kilojoules, which works out to about 2.2 megajoules per kilogram. that's a substantial amount of energy
because of gold's extreme nobility people usually complex it with cyanide or thiourea in order to do things like electroplating. its standard electrode potential to go to metallic state from the dicyanide complex is only -0.6 volts. but i don't know what form it's in in the oceans
______
† these potentials are all under standard conditions: unit activity for every reagent, 25° temperature, one atmosphere, etc. things like acidity and temperature can shift them a bit; https://en.wikipedia.org/wiki/Pourbaix_diagram is all about how they change with acidity, for example. but i don't think there exist conditions extreme enough to electrowin metallic vanadium or titanium
That is as close to alchemy as we’re probably ever gonna get then!
No, closer to alchemy is the actual creation of gold from other elements with nuclear physics.
Was demonstrated quite a long time ago, but is not really practical to get meaningful quantities out of it.
(That is why I always prefered physics over chemistry - my chemistry book in school started with the story of the alchimists and concluded that they were bound to fail as gold cannot be created.
And in my physics book was just the formula to create gold)
> No, closer to alchemy is the actual creation of gold from other elements with nuclear physics.
The place where this happens is in the liquid mercury target of the Spallation Neutron Source at Oak Ridge. Here, high energy protons shatter (spall) mercury nuclei, producing fragments that can include gold. An uncommon isotope of mercury can also be converted to gold by neutron capture.
Is it the stable isotope? I understood that the only place to get that was neutron star collision but I would love to know more if wrong.
Yes, this can produce the single stable isotope of gold. Not in any practical way, though. It would be cheaper to just mine more of it.
> is not really practical to get meaningful quantities out of it.
you can build the entire neutron spallation reactor out of materials much cheaper than gold, and you can get unlimited quantities; the only impracticality is that the humans are still really bad at building machinery
Well, there's the excuse I need to build a Farnsworth fusor, I guess.
> not really practical to get meaningful quantities out of it.
It is quite practical. You just pour a big pile of hydrogen out, let gravity compress it until it starts fusing. Initially it will only create helium but near the end of the pile’s life you will get mountains of the other elements too.
Easy breasy. It just takes time and quite a bit of space and hydrogen. Much harder to scale it down of course. But think big and aim for a star as they say.
‘Natural’ fusion will only get you as far as iron. Supernovae may produce heavier elements, but the heaviest elements like gold are probably produced in neutron star collisions.
https://en.wikipedia.org/wiki/Nucleosynthesis#History_of_nuc...
Supernova explosions are good enough to make gold (and most other heavier elements until plutonium) by neutron capture.
Fusion, as you say, produces quantities that diminish very quickly for the elements beyond iron (iron 56 has the greatest binding energy of any nucleus and the binding energy decreases slowly after it), so that the last element that is produced in non-negligible quantities by fusion is likely to be germanium.
Not really I think, as this is not transforming something else into gold, it just kind of lumps existing gold together (if I understood the article correctly).
We have a name for that kind of alchemy - nuclear fission/fusion.
Because gold is so inert (a noble metal) its counterintuitive to see it in other forms eg in solution. In that sense manipulating gold in other forms than its elemental form probably feels like alchemy in common parlance.
I know aqua regia is relatively normal but I still find it weird to think of gold being dissolved
Gold is difficult to oxidize, but once oxidized it has some of the biggest ions, which stay easily in solution if no reducing agent is present.
The ion Au(I) has about the same size as the ions of potassium (which are exceeded in size only by cesium, rubidium, thallium and radium).
The ion Au(III) has a more normal size, but it is still relatively big, similar to the trivalent ions of the rare earths.
The big size of the gold ions is one of the reasons why its combinations with small ions, like oxide and sulfide, are unstable, so you cannot find such minerals in nature.
On the other hand, the gold ions form stable compounds with bigger ions, like telluride. Therefore there are many minerals where gold is combined with tellurium (unlike silver and copper, which combine with the smaller sulfur).
Nevertheless, on Earth tellurium has an abundance almost as low as gold, even if tellurium is abundant in the Solar System. The reason is that tellurium is easily vaporized, so less of it has condensed when the Earth has formed and a good part from what has condensed initially has been lost later, when the Earth has been heated by many asteroid impacts during its early history.
While tellurium is rare because it went up, being lost as vapors, gold is rare because it went down and most of it is dissolved in the iron core of the Earth. Because both tellurium and gold are very rare at the surface of the Earth, the chances of them meeting together in amounts great enough to form a mineral are very low.
The result of this scarcity of tellurium on Earth is that most of the gold can be found as native gold and only a smaller fraction is found in compounds with tellurium. Had tellurium not been lost from Earth, the amount of native gold would have been very small, similarly with the much smaller amounts of native silver and copper that exist versus the amounts available in sulfide minerals.
Thanks for sharing this - excellent content. I've been out of the game for a long time now but isn't this just the case that Gold is too soft as an ion to mix well with stuff like oxides?
Cs(I) should be larger than Au(I) but it seems to form a comparatively stable oxide Cs2O. But yes Tellurium is also a nice soft element so AuTl have a good affinity for one another.
Was unaware of their chemistry, it doesn't even ring a bell tbh I wonder if I had ever encountered it before. I did enjoy studying the Post Transition Group Metals back in the day
Yes, as I have said, size is only one of the reasons of incompatibility with oxide ions.
As you say, gold has a much higher electronegativity than cesium and rubidium, i.e. not much lower than that of silicon, which makes it a "soft" ion, and that reduces the stability of any compound with oxide or hydroxide or fluoride ions. On the other hand, the incompatibility with the "softer" sulfide is mostly caused by the size ratio.
Aqua Regia is relatively normal in the sense that being threatened with a knife is relatively normal.
If you think it is, you’re probably hanging out in a pretty bad neighborhood. But yeah, most people won’t be surprised it exists.
Well I'd argue getting threatened with a knife is relatively normal in London but that's off topic :)
Aqua regia is not particularly exotic as compared with all the fancy ways you can harm yourself or react things in Chemistry. You can probably prepare it at home using stuff that might be buyable over the counter.
Getting your hands on things like azides or Polonium 210 or having access to a nuclear reactor to do ad hoc fission/fusion is a lot less normal on that scale.
Additionally aqua regia has been known for quite a long time, from before we even knew about gases
Fwiw I forgot what the magic cleans everything mix was but I want to say it was H2SO4 and cif which we'd just squirt around in our fume hoods
For sure! Cleaning solution, you’re thinking Piranha solution probably.
Aqua Regia definitely isn’t exotic (same as getting threatened with a knife), but also isn’t going to be nice to be around, and getting ‘cut’ is pretty easy if you don’t pay attention.
And either one are frowned upon at most dinner parties. At least the ones I’ve been to, but I try not to judge ;)
Ha yeah I think it was called Piranha solution - thanks for the nostalgia! :)
Yeah you're right getting threatened by a knife isn't very exotic
Bad neighborhood like Nazi Germany? And suppose you're Niels Bohr? How should you hide those Nobel prize medals...
Obviously my comment was meant in jest, but I still think your typical 17th century alchemist would be quite convinced you've figured out Chrysopoeia if you showed them this process—even if it's just lumping trace amounts of gold together.
This isnt a new hypothesis
Several years ago I had read something similar about gold in underground water reservoirs forming along the walls based on … essentially earthquakes
Fred Hoyle wrote a pop sci book in the sixties talking about how things worked in early earth formation with prosaic imagery of gold squeezing around in quartz.
So , alchemists might had discovered that somehow ?
they did have aqua regia, and crystallizing previously dissolved gold from it was, as i understand it, commonplace
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