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Since the most aboundant elements by weight on Earth's crust are:

  • Oxygen 46.6%
  • Silicon 27.7%
  • Aluminum 8.1%
  • Iron 5.0%

Would it be possible to build an entire city out of just these elements? So, for example, glass would be OK because is mainly made of SiO2.

The city must have:

  • Tall buildings (>20 floors)
  • Transport
  • Electrical energy network (don't need to produce it though)
  • Communication network (Internet access)
  • Water and Drain system

All other non-infrastuctural objects (food, clothes, forniture, appliances, etc.) and living beings are allowed

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Some ideas

Buildings: can the buildings be made out just of Al/Fe or an alloy of them?

Transport: maybe transport by train can be acheived?

Electricity: Al can be easly used as a conductor and some glass fibre as insulator.

Telecom: wireless or Al

Water: I would say Al again

Aluminium is very versatile indeed :D

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  • $\begingroup$ It'd be very expensive, but I think that how you described it would work perfectly fine. $\endgroup$ – Pedro Et Cetera May 4 '17 at 23:07
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    $\begingroup$ I'm not 100% sure if the degree of miniaturization and precision that modern day cities need (electronics for example) can be achieved with just these elements (can we do laser precision tools with just these elements?). Can we assume they have access to other elements to create the city, but in the end the city must only be these 4 elements? $\endgroup$ – Twelfth May 4 '17 at 23:14
  • $\begingroup$ Whatever your transport system is made out of, it could be propelled by liquid oxygen. $\endgroup$ – highpriestofpie May 4 '17 at 23:24
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    $\begingroup$ Not sure if I could get a battery out of just these elements which would make powering remote devices a challenge. Aluminum will function for electronics, but really not well. High resistance being the biggest issue here (about 40-60% as conductive than copper). Aluminum makes a poor antenna too, I don't think you could arrive at wireless with just this. $\endgroup$ – Twelfth May 4 '17 at 23:27
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    $\begingroup$ No. You need at least hydrogen (for water), carbon (to make steel), sodium (to make usable glass) and calcium (for cement and concrete). Copper would be nice too. $\endgroup$ – AlexP May 5 '17 at 1:14
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No mostly becasue pure aluminum and pure iron and pure glass are useless

Non-additive glass in general is a poor choice for almost anything except optics. You certainly would not want to build anything out of it.

Pure iron and pure aluminum both corrode very easily, they are also both soft and weak, if you built a telephone pole out of either it collapse under its own weight. there is a reason we use nothing but alloys. The brinell hardness of pure aluminum is 15 and the pure iron is 20-30 depending on crystal structure. For comparison electrical copper is 42 and mild steel (0.05–0.25% carbon) is 120.

But you could easily make a show city where those four elements are very prominent.

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    $\begingroup$ What about this Fe-Al alloy? It says it's as strong as Titanium. gizmodo.com/… $\endgroup$ – bcl May 5 '17 at 8:09
  • $\begingroup$ Also Silumin is resistant to corrosion: en.wikipedia.org/wiki/Silumin $\endgroup$ – bcl May 5 '17 at 10:45
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    $\begingroup$ Fe-Al alloy is not just Fe and Al, it also contains nickel and carbon. Silumin is similar it also contains copper and magnesium. $\endgroup$ – John May 5 '17 at 13:42
  • $\begingroup$ You would have to add carbon (for steel) and copper to the list, at the very least, if you can live with no integrated circuits. $\endgroup$ – Dan Fernandez May 5 '17 at 19:43
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Im going to have to give a conditional no answer. The biggest thing lacking is a usable element for electrical purposes. Most aluminum wiring has been removed from modern cities as it is ultimately a poor conductor when compared to copper or silver. Its not that aluminum doesnt work for these purposes, its just horribly inefficent. There is a reason why telephone cables are referred to as copper pairs.

Im also at a loss to create a functioning battery using this elements. Remote electrical devices likely wont be a possibility if its considered part of the infrastructure. Wireless communication is also unlikely, mostly due to the reasons above, aluminum and irom make horrible antennas.

Most of your other points should be feasible though. Oddly enough, if you were to add copper or silver to the mix (5 element city?) i think youd be close to feasible.

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  • $\begingroup$ I don't know about a battery, but the elements are sufficient for thermite, so the storage of energy is no problem! $\endgroup$ – Cort Ammon May 5 '17 at 0:19
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    $\begingroup$ Aluminum is actually a better conductor than copper by weight; copper is a better conductor by volume. For example, overhead power cables are often made of aluminum, because for overhead cables weight is more important than the volume. $\endgroup$ – AlexP May 5 '17 at 1:18
  • $\begingroup$ I believe you are wrong. Without carbon there is no steel, and without steel and concrete tall buildings are next to impossible (as answered by John). Thus, electricity is a non - issue in a way that there will be no buildings to electrify. Even street lamps on poles would be difficult to make. $\endgroup$ – Mołot May 5 '17 at 7:36
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    $\begingroup$ @Twelfth: That's exactly what I said; by volume copper is the 2nd best electrical conductor (the best is silver). However, in certain applications, such as high-voltage overhead lines, volume is much less important than weight. So, in such applications, aluminum is preferred, because although it has a conductivity about 1.7 times lower than copper, it is 3.3 times less dense: which means that a conductor made of aluminum will be about 2 times ligher than a conductor with the same resistance made of copper. $\endgroup$ – AlexP May 5 '17 at 19:10
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    $\begingroup$ @Twelfth: For some applications it works for others it doesn't. For an application where aluminum works, see the Wikipedia article on wire bonding. $\endgroup$ – AlexP May 5 '17 at 20:15
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The other answers already raised some good points, here is another one against it, from a different direction:

Nobody would ever build such a city. It is almost impossible and certainly not financially viable to make things out of these elements only without an significant amount of impurities and even if you managed to do that, what would the benefits be? This would make your world completely unbelievable, so you can basically just invent anything and say they made a computer with a display entirely out of different modifications of SiO2.

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    $\begingroup$ True, it's just a mental exercise. If you find a way, you could build unlimited cities like this and never run out of resources. :D $\endgroup$ – bcl May 5 '17 at 14:17

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