Gold and silver is less common in space than here on Earth.
Nevertheless, in the crust that covers the surface of the Earth, the abundances of gold and silver and of platinum-group metals are many orders of magnitude lower than their average abundances in the Solar System.
For instance most of the silver has remained in deep parts of the mantle when the crust has formed, so silver is 11 times less abundant at the surface of the Earth than in the Solar System.
Gold and the platinum-group metals have gone to even higher depths, in the iron kernel. So at the surface gold is almost 300 times less abundant than in the Solar System, rhenium almost 600 times and nickel more than 900 times less abundant than in the Solar System, palladium around 3000 times, platinum and ruthenium around 5500 times and osmium and iridium around 50000 times less abundant than in the Solar System.
Similar numbers apply to all of the 8 planets that are big or medium-sized and also for some of the small planets and big satellites, because all these have been melted at some point in their history, when all the metals with high affinity to iron or sulfur have gone to inaccessible depths below the surface of those planets.
In the outer parts of the Solar System, the bodies are covered by thick layers of ice, but for the 4 inner planets the silicate crust that we see covering their surface is similar to the slag that forms at the surface of the iron smelted in an iron furnace and it is similarly depleted in the metals with low electropositivity.
16 Psyche might, or might not, be such an object. If so its surface is still covered by a "rubble pile" layer of rocky material.
https://www.space.com/james-webb-space-telescope-psyche-plan...
While the depletion has reduced the amount of platinum-group metals by many thousands of times, the enrichment only increases their concentration a few times over the average concentration.
The reason is that the planet cores still include iron, one of the main 10 elements of the universe, the least abundant of which is many times more abundant than all the other elements combined.
The enrichment consists only in the removal of the magnesium, silicon and oxygen from the planet core, while the iron stays there.
Even with all the platinum-group elements in the core, their abundance cannot increase beyond the limit imposed by the ratios between their average abundances and that of iron (actually their abundances become a little larger than those ratios, because a bigger fraction of iron remains oxidized in the mantle than the corresponding fraction of platinum-group metals, but the difference above the average ratios remains very small).
You sure about that? Here's just one asteroid made of mostly gold, nickel, and / or iron that's supposedly worth many times more than the entire global economy. Pretty sure that anything we have here on Earth also exists "out there" in much greater abundance than we could ever possibly imagine here on our finite little speck of a planet (except maybe "life", which we only have absolute proof of here on Earth).
However the Earth is made of layers with different chemical compositions and many elements are concentrated in layers that are too far from the surface to hope that we will ever reach them. So in the accessible part of the Earth, close to the surface, those elements are seriously depleted.
Some asteroids, unlike the Earth, have never been melted. In that case their composition is homogeneous, similar to the averages of the Solar System. Other asteroids are broken parts from the cores of bigger planets, so they have a composition like in the Earth at very high depths.
However, in the latter kind of asteroids the useful metals are dissolved as tiny percentages in an iron-nickel-cobalt-germanium alloy. This will make their extraction incredibly energy-consuming. On Earth such metals have been separated during millions of years from their surrounding minerals and they have been accumulated as native nuggets or metallic sulfides that are very easy to process for their final separation and purification.
With the alloy that exists in planet cores and asteroids nobody has demonstrated an efficient separation method yet. The laboratory methods used for such separations use huge amounts of water and acids and they will be impossible to implement on an asteroid. Carrying raw metal from asteroids, which is almost completely iron, would also increase the costs tremendously.
So it is absurd to even consider asteroid mining before demonstrating a method that can extract the metals from iron at the mining sites and with a minimum consumption of energy and of non-recyclable reactants.
You hear these statements sometimes about asteroid mining, and they betray a misunderstanding of the way economies work. The reason gold/etc. is expensive is because it is scarce. If we suddenly have an abundance of these materials, then they will be cheap. The intrinsic value of these metals is not worth multiples of the global economy.
Even with/if there's a 'flood the market' eventuality, you'd have approx multiple generations for the market to grow and mature, improving the associated technologies along the way, and wealth generated orders beyond the Carnegies Rockefellers and Vanderbilts combined.
Also, not sure why the prior comment was gettin' down-voted. I'm just tryin' to be encouraging here. If this guy has an idea and wants to write, I'm just sayin' "go ahead and do it then". Why not? Even if nobody ever reads it, if you enjoy writing it, then something was gained.
They are extremely numerous, but most of them are extremely small. Changing the spaceship orbit to catch one of them, which might have a few tons only in rare cases, will provide only a few grams at most of useful elements, far too little for the energy spent to achieve this.
Mining a big asteroid that is a fragment of the core of a former bigger planet has much more chances to be worthwhile, but even for that nobody has gives any suggestion yet for how to separate the mined metals from iron and nickel at the extraction place, otherwise the transportation of the raw alloy would also need too much energy.