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According to an answer to a previous question, it would be comparatively impractical to conduct mining on a rocky planet when there are moons, asteroids, comets, etc. that have smaller mass, so much less fuel would be required to reach their respective escape velocities. Thus, mining would be less cost efficient and generally avoided on rocky planets, if possible.

Let's suppose that these spacefaring mining operations were launched to obtain one particularly valued mineral as opposed to general resource exploitation. Because the setting is intended to be a single rocky planet, why might this mineral be found exclusively on said planet (or at least, it has not been discovered elsewhere after reasonably thorough prospecting) and no other bodies in the solar system?

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    $\begingroup$ Only if the laws of nature are different from those in our universe. If a mineral exists on one planet it should exist on any similar planet. Hypothetically the mineral might only be found a rare type of planet. A challenge to work out what that would be. $\endgroup$ – a4android Aug 16 '17 at 13:14
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    $\begingroup$ How does one know where to mine for minerals? Experience. There isn't a magical machine that geologists use to determine where minerals (or other things underground) are, this is hard work. If you were lucky to find one mine of such a mineral and that required lack experience (maybe for example with the geological features of other worlds) - well, there you go ... $\endgroup$ – Raditz_35 Aug 16 '17 at 14:42
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    $\begingroup$ Don't be in a hurry to forget the luck factor. There's a fair amount of evidence that there is WAY more water on Earth than can be explained without an intervening stellar impact. Also, FYI, there is as much or more Uranium in the Earth's crust than there is Tin, but much of it is wildly impractical to extract. The mineral doesn't have to be unique per se; it just has to be the only practical, economical source. Those considerations should free you up a bit. $\endgroup$ – Sean Boddy Aug 16 '17 at 15:51
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    $\begingroup$ Planet where "third of the planet's mass might be pure diamond" en.wikipedia.org/wiki/55_Cancri_e $\endgroup$ – Jan Ivan Aug 17 '17 at 8:35
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    $\begingroup$ You don't need the mineral to only exist on that planet, but to only exist on that planet in useful concentrations. A handful of dirt from your garden will contain uranium. But in order to mine uranium you want a concentrated vein. The difference between "ore" (dirt from which stuff you want can be extracted) and "dirt" (dirt from which stuff you want can't be extracted) is purely economic. After extracting the stuff, can you sell it at a profit? Or in a post-money society - is the value of the stuff greater than the value of the effort spent getting it? $\endgroup$ – Grimm The Opiner Aug 17 '17 at 9:58

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Organic

Your mineral could have been deposited millions of years ago by a specific type of organism, class of organisms, or type of biome. For instance, you might have a forest that produces lots of some interesting organic compound, which when put under intense pressure and heat, forms some mineral with useful properties. Because the relative scarcity of "live" planets, you might only have access to one such planet, or another with the same phenomena might be too far for mining to be economical. Furthermore, there is no reason why the same biological phenomina must occur on more than one planet in a finite range (that range being the reach of your civilization). Planets with life are just so much more fun, so much more interesting, but they aren't the only option.

Inorganic

Your planet could have been formed from a unique mix of stardust. Maybe it has a lot of superheavy stable atoms in its crust. Perhaps it has interesting temperature or magnetic conditions that caused unique geological formations. I can't really tell you what exactly you ought to choose as your reason, but the possibilities are endless. Ask your friendly neighborhood planetary geologist.

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Access and Sensing

Unless your civilization has found a way to travel, for free, instantaneously from one point to another, anywhere, then there is a cost to travel. The range of planets you can harvest from is first limited by the planets you can find, then by the planets you can reach, then by the planets you can scan, then by the availability of the resource on the planet. A perfect planet might exist, but be too far away. This resource could be on your planet, but it could be too difficult to collect. You can change the parameters of this equation in whatever way you like, but it will still affect the collection of resources in any system to a certain degree. Hell, if you are a sensitive bunch, then you could even honor the claims of existing beings to resources (hello blue people with tails!), the claim of future beings to resources, or even the sanctity of planetary integrity. There are so many barriers to access that we can think of now, but what we can think of now is probably much, much easier than it would be in real life.

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    $\begingroup$ You don't even need the mineral to be organic to be biological in origin. In fact, many of the minerals on earth might be due to life, even the ones you normally think of as "abiological" in origin. It's not that organisms make them directly (though that happens), but that life alters environmental conditions enough to make it possible for these rare minerals form. $\endgroup$ – R.M. Aug 16 '17 at 16:05
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    $\begingroup$ Note Dune books have exactly this premise. A unique substance which is due to biological factors. $\endgroup$ – Wes Aug 16 '17 at 16:47
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    $\begingroup$ Of course, I didn't even think of that. Additionally, organisms can be a condenser of matter, such as carbon sequestration in Algae and green plants. $\endgroup$ – Dent7777 Aug 16 '17 at 16:49
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    $\begingroup$ Coal and chalk are great examples of valuable rocks with a biological origin. their components can occur without biology but their combination, structure, and concentration which make them valuable are all products of biology. $\endgroup$ – John Aug 16 '17 at 17:03
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    $\begingroup$ Don't forget pressure requirements, e.g. Some planets might not have the right conditions for diamond formation $\endgroup$ – somebody Aug 17 '17 at 7:04
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Heavy Metals.

The heavy and rare elements can be produced in Supernova; things like Gold, Platinum, etc. There are other ways, but precisely how isn't important.

But, they can produce them in massive quantities; then heat, explosive forces and gravity can "refine" them to some extent, sorting them by molecular weight. So you can have something like asteroids made entirely of these heavy metals; or even primarily one, like Gold. The Gold on the surface of earth most likely arrived by such asteroids; because any that was present during the planets early molten formation likely sank toward the core.

One planet in the solar system, or even in a large region of solar systems, might be the lucky recipient of such a treasure (gold, platinum, uranium, osmium, etc, see the link above).

Probes might be able to sense the presence of such heavy metals, and as a result the miners are stuck with wherever it might have landed, whether that is Earth-sized or Jupiter-sized, as hot as Mercury or cold as Pluto.


Added to address comment: Here is a Harvard study (from 1956, but still relevant) discussing the predominance of elements in Stars, in Terrestrial abundance, and in meteorites (see pages 187, 192, 194). It is simply untrue that it would be better (more cost effective or easier) to mine common asteroids than it would be to mine a large planetary deposit of some rare metal. Gold in asteroids has a concentration of about 1 part per 20 million; while the top gold mines earth are rated in the 25 to 44 g/t (grams per metric ton [which is 1 million grams]), so 25 to 44 parts per million: That is 500 to 900 times greater concentration than one might find in asteroids.

This is one contributing factor supporting the hypothesis of a gold-heavy asteroid; plus the concentration of high yield gold mines is primarily in Africa: suggesting a rather localized event (or events, if the asteroid broke up) deposited the gold in spots after the formation of the planet; it is not a uniformly distributed element.

For the purposes of a story, there is no reason this could not be amplified; that the miners are specifically seeking extremely high concentrations of precious heavy metals that have some commercial utility. It would be plausible for them to look at rocky planets and moons that might have captured such asteroids in the last few billion years; and somewhat preserved the deposits where they landed. It would be easier than testing billions of asteroids that are probably worthless, and easier than processing 1000 or 2000 times the mass in asteroids looking for some atoms of gold or uranium or osmium or whatever they are seeking. They might not even have the technology to extract a milligram or microgram of an element from a one tonne rock; they may require a higher concentration to make it worth their time and effort (just like our modern day gold miners do).

Finally, they may have far more efficient and cheap means of getting on and off planet; like fusion engines that cost effectively zero. Energy is generally not a problem in space, stars generate plenty of it. They could have huge solar generators in space that beam all the energy they need down to the surface in the form of gamma ray lasers or something. And once they finish mining, they only need to get the product out of the gravity well, not the million tonnes of rock they crushed. The robots they are using to do the mining may weigh far more than the final product they extracted, particularly for very rare elements. And again, the energy needed could be absolutely free to them; captured from the star (even we humans know how to do that IRL).

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    $\begingroup$ This -- the earth has plenty of "rare" metals. It's just that they've sunk deep into the Earth because of their weight. They're so far down it would be cheaper to rope in asteroids and mine minerals from them. $\endgroup$ – user151841 Aug 16 '17 at 15:01
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    $\begingroup$ So.... Gold is on earth and not on asteroids because it arrived via asteroids? And you are comparing average density in asteroids with the very best mines earth has to offer? $\endgroup$ – ths Aug 16 '17 at 18:18
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    $\begingroup$ @ths Part I: Not all asteroids are identical. Gold (and other heavy metals) get created by supernova and expelled by the explosive energy in huge lumps of matter. 99.99999% of asteroids are silica and other worthless elements; rock. Earth likely has concentrated pockets of gold on its surface due to being struck by a multi-ton large lump of it arriving from outside our solar system. Technically an asteroid but unlike 99.99999% of asteroids. The chance of finding a gold asteroid orbiting our sun is astronomically small, and surface gold on planets is likely extremely rare. $\endgroup$ – Amadeus-Reinstate-Monica Aug 16 '17 at 18:49
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    $\begingroup$ @ths Part II: yes of course I am comparing it to the very best mines on Earth; that is the whole point. Professional miners, both on Earth and fictional ones that can mine whole planets, seek out the highest concentrations of whatever they mine. The gold density in asteroids that all formed with our solar system is probably extremely uniform (meaning a very small standard deviation). The same would be true of planets, except that some planets can by chance catch a whole mountain of gold, platinum, uranium, osmium, etc, resulting in a high concentration worth mining. $\endgroup$ – Amadeus-Reinstate-Monica Aug 16 '17 at 18:55
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    $\begingroup$ You appear quite fond of the hypothesis that high concentration gold deposits were made by some large, high-purity gold asteroid. I consider that to be very unlikely to be the primary cause of gold concentration. I suggest that you read up on various geological processes, including the genesis of ores, including gold. In general, the more commonly held theories are that gold concentrations are created through plate tectonics, geochemistry, weathering/erosion/sedimentary processes, etc. $\endgroup$ – Makyen Aug 17 '17 at 1:42
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Access.

Even if a particular resource is found in other places, that doesn't mean that it is accessible and practical to acquire. So only single site may be reachable, hospitable to miners/robotics, have nearby resources also required for mining/fuel/energy, be in an area secure from competition, and reachable in a useful amount of time. There may be only be one known place where the resource is in a high enough concentration to make mining/gathering it financially worthwhile.

The Avatar movie had this premise. I'm sure the unobtanium macguffin element was present in other places, but the Pandora moon was reachable, allowed miners to survive there, and was reasonably close to Earth so it was worth the investment to gather.

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As @Dent7777 stated, materials like oil are organic based so it's almost impossible to find in other celestial bodies.

If you're talking about an inorganic material then I feel like the 'planetoid from an unknown solar system composed of X material crashed with the planet in its early years' like the Theia hypothesis would work.

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An obvious answer is that the mineral is artificial, made by an unknown ancient civilization in great quantity for reasons unclear, or as an unintentional byproduct of some other process.

It is possible that the process of manufacture was an automatic one which ran out of control and brought about the end of the civilization before it could be stopped.

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    $\begingroup$ E.g. Chernobylite. (The harder question is why it would be valued). $\endgroup$ – Peter Taylor Aug 16 '17 at 19:56
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Read the novel Mirkheim by Poul Anderson. It concerns a planet that was just far enough away from a supernova explosion to survive, but acquired a significant amount of super-heavy elements in the (hypothetical to modern-day science) island of stability, that were created in the explosion. You need FTL interstellar travel for that, of course; a planet in our solar system won't fit the bill.

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One fairly obvious reason is concentration. Many useful minerals can be extracted only because they've been concentrated in veins/ore bodies through billions of years of gelogical processes. Many of these processes are geothermal: they require the planet to have both a hot interior and plenty of liquid water.

So your useful material - say gold, for a common instance - might exist on moons & asteroid, but like gold in sea water, in parts per trillion amounts. On an earthlike planet, that gets concentrated into gold-bearing veins by geological processes, then erosion further concentrates it into placer deposits, and then a guy building a mill can pick up nuggets and start a gold rush :-)

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Lots of good answers, but nobody's mentioned metamorphic minerals. There are lots of mineral substances that are formed via the intense heat and pressure under the surface of a planet. Asteroids and small moons do not generate nearly as much heat and pressure. You're much less likely, therefore, to find significant deposits of marble or diamond in an asteroid field unless the field was originally a planet large enough, that existed long enough for such substances to form prior to it disintegrating.

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In Earth, there are some elements that are rare on the surface because they're heavy, and sunk to the center of the planet when it was still a molten ball of magma. The best example I can think is iridium, which isn't that rare on our planet, but most of it is deep down in the mantle. Only a very small fraction of it is distributed on the lithosphere.

The planet in question could have formed in a very peculiar and rare circumstance, in a fashion that allows the formation and easy mining of hard-to-form minerals. It could be, for example, a small rocky planet around a metal-rich red dwarf star, which coallesced, cooled and solidified very slowly, so the chemical elements distribution is fairly even all around. Or, the opposite, a planet that cooled and solidified so fast that heavy minerals hadn't time to sink to the core.

In both cases the presence of rare elements near the surface would allow the growth of crystals or ores that we simply don't get here, like samarium crystals for example.

Yet another idea can be a Roche world, a double planet where the planets orbit so close to one another that they've exchanged material between them when they were balls of magma, essentially creating a peanut-shaped double planet with a rocky bridge between them. It couldn't be hard to mine this bridge section for rare minerals.

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Similar to @LeeLeon's answer...

What if an ancient space faring civilization has already mined the material from every available source within your civilization's reach; concentrating all that they collected on their home planet where it was valued and revered.

If that civilization then collapsed and the ravages of time slowly erased all signs of their existence, you might find a apparently undeveloped planet loaded with the material to the exclusion of all other planets in the area.

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This might stretch the definition of "mining", but if we allow aliens, you could be scavenging alien trash or building materials.

Imagine for a moment if an ancient human civilization were to find one of our abandoned cities. Even our simple building materials (steel, aluminum, plastic, and glass) would be valuable. It could be that when our scouts get to Pluto, they find a large alien outpost that was abandoned, made of a amazing material, that we don't have the tech to reproduce, but we can shape.

If you want to make it more like mining, and restrict access to the original tech, you could have the aliens drop an asteroid on the base before they leave, only leaving pulverized materials that can be "mined" but aren't much use otherwise.

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The Oxygen Catastrophe/Great Oxygenation Event was responsible for one of the most significant extinction events in Earth's history. It is also estimated that the Great Oxygenation Event alone was directly responsible for more than 2,500 new minerals of the total of about 4,500 minerals found on Earth.

There are a number of articles, such as this one, that state that human activity is producing new types of minerals.

All you need is some plausible, unique, large/long lived event to potentially be the trigger for exotic minerals in sufficient quantities to make mining reasonable.

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The previous civilization's nuclear program

There was once a civilization on that craggy rock, and they had a rather robust nuclear program, in which they synthesized a lot of different atoms. A lot.

Many of them decayed into the rare element you want, and are stacked up in their former nuclear waste dumps (which are now largely inert due to countless millennia of decay). Or, they may be scattered all over the planet from a little... thing they did.

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The way I see it you have two real options.

A super rare organic material

Coal for example. Not rare on Earth, but rare in the solar system. Maybe even rare in the galaxy. You need carbon based life and a long time to make coal so it's not going to be abundant.

A common but you need a lot of it material

Heavy metals are a good example. There common because they can be found many places, but you need tons of the stuff.

Things to avoid

  • Don't choose a material that is only on one planet. That always seems off. If one planet has it then others do.
  • Don't base off rarity on earth, Coal is a good example. It's really common here, but no where else in the solar system.
  • Don't worry about "carry weight" or launch weight. If you need the material then even if you have to spend huge amounts of energy to get just a tiny bit of it, we do that on Earth. Using what you mined is ok too. Even if you use 90% of what you mined just to get 10% in to orbit, that's ok if there is no other way to get the fuel.
  • Stay well away from things like gold, silver, etc. The material you choose needs to have a real use. Mining gold for wires for example could be a by product of the coal mining process. But it's the coal your after.
  • Don't rely on gimmicks like "odd solar radiation" to create your material. Unless that part of your story. Stick with "other places have some but this place has more."
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There are so called rogue stars, or intergalactic stars. This is a star that has escaped the gravitational pull of its home galaxy and is moving independently in or towards the intergalactic void. I could imagine a rogue star scraping a planet boiling off the outer layer of the planet and blasting said layer away, leaving a planet made mostly of metal.

This would make it very productive to mine, and the planet might have some interesting properties. I imaging it cooling a lot quicker because of the high heat conductivity. You might be able to traverse the planet with maglev vehicles.

The interaction with the rogue star would likely launch the planet itself away from its host star. If it's on a path that's eventually passing one of your planets you could start to mine it, and when both planet are nearest to each-other move all the metals to your home planet.

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  • $\begingroup$ Why a rouge star and not just another star in the same galaxy? $\endgroup$ – lijat Aug 18 '17 at 16:19
  • $\begingroup$ I figured the paths of the stars in a galaxy that bob happily around their home galaxy don't cross other stars. But now I think about it that isn't right, because such a inter-star event is how a rogue star comes to be in the first place. Good point. $\endgroup$ – Herman Aug 21 '17 at 7:27
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The mineral is produced by an organism in some way, either as a byproduct (such as from its remains/excrement etc) or for some purpose to the organism (nest building, to feed to its young etc).

The chances of the exact same organism evolving on another planet are so remote that for all intents and purposes it can only be found on your planet.

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Maybe an ancient civilization produced/mined/extracted/(or even fetched this mineral from a distant planet), and some apocalyptic event has wiped out that civilization.

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  • $\begingroup$ Welcome to WorldBuilding! Thanks for taking the time to answer this question, but usually people are looking for more research. If you want to give a small suggestion you could consider leaving a comment on the question instead. If you have time and haven't done it already, feel free to take the tour to familiarise yourself with the site, and visit the help centre for other information $\endgroup$ – Aric Aug 18 '17 at 15:02
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Why might a precious mineral only be found on one planet? It isn't. The universe is too big for that.

In reality it's only found on one planet that you know of because of rng. Alternatively, if you don't like rng, it's only accessible and cost effective on one planet. Tectonic activity could easily explain this.

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