Natural Piezoelectric Effect May Build Gold Deposits
arstechnica.com
arstechnica.com
Quartz crystal array + electricity -> gold layers?
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.
> 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.
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
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† 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
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)
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.
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
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.
https://en.wikipedia.org/wiki/Nucleosynthesis#History_of_nuc...
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.
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
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.
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
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.
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.
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
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 ;)
Yeah you're right getting threatened by a knife isn't very exotic
Several years ago I had read something similar about gold in underground water reservoirs forming along the walls based on … essentially earthquakes