Eli5 why is aluminium not used as a material until relatively recently whilst others metals like gold, iron, bronze, tin are found throughout human history?
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There is an aluminum pyramid at the tippy top of the Washington monument, construcfed in 1884. They put it there because aluminum was incredibly rare and incredibly expensive at the time. More so than even gold. We didn’t figure out till a few years *after* that how to reliably extract it from the earth in a usable form.
It’s hard to make aluminum, it’s not found in metal form like copper and gold. It also can’t be smelted into metal with coal like iron or tin.
Until electricity became widely available and cheap there was no industrial production method, just lab-scale methods. Even the lab methods required metal sodium or potassium which in turn also needed electricity to make.
Aluminium oxidizes extremely easy. And it will stay oxidized unless you do dramatic things to it. Your other examples are much easier to refine. Gold does not normally oxidize so you can just pick it up from the ground. Tin and copper (bronze) can be refined just by heating it in an oxygen poor environment, such as a camp fire. Iron requires somewhat more heat and needs to react with coal to form pure iron from iron oxide but even this is relatively easy. However aluminium can not be refined in this way at all. Even today we can not refine aluminium this way. Aluminium is refined using electrolysis which requires huge electric power plants nearby. So we needed to find up electricity before we could start mass producing aluminium.
We did however use aluminium oxide for various things before we used the metal. It is an excellent abrasive which is used in for example sand paper. So we did mine aluminium and there are actually some very cool advancements in chemically separating ores which were first invented for aluminium. And there are actually a couple of extremely rare aluminium artifacts from the middle ages which we do not know how were made. But the rarity of them suggest that it was not something done at any large scale, each item was likely the lifes work of several people.
Aluminium is found in nature as bauxite basically aluminium oxide and can’t be processed easily into aluminium.
Because it was only discovered in the 1820’s.
And when it was discovered, it was extremely expensive to make (in fact, kings would put out aluminium cutlery to impress peers, while everyone else got cheap gold forks!)
Over time, the process was refined and aluminium became affordable so is now used in many applications.
Before the [Hall-Heroult process](https://en.m.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process) came about, there was no cheap, easy way to take aluminum out of ore (where it’s all found) and turn it into mostly pure metal.
The process to pull aluminium out of the ground and refine it requires a good amount of science and is a multi level process. And its expensive.
Other metals you mention are relatively simple and can be refined in crude ways.
However, the process to make aluminnum is worth it because Aluminium can be recycled an unlimited amount of times. As it never loses its integrity after its melted down and formed into different shapes.
Other metals like tin, iron and copper become too weak after being re-used and melted down after too many times.
For aluminium, a can of pop recycled can become a part of a car engine. 20 years later can be melted down and turned into a component in a aeroplane’s landing gear. 20 years later can be melted down into foil for sandwich wrap. And if that wrap is salvaged it can end up again as a painter’s ladder. And if that ladder ends up being recycled it can end up a piece of medical equipment or back to a pop can.
And if someone took a piece of that pop can took and put it under a microscope the molecules will look the exact same from when it was first refined 100 years earlier.
Its truly magical.
Because converting the raw material (Bauxite) into something useful was not something that was easy or cheap until the Hall Heroilt process was discovered. It is the same with steel. Some of these processes are very energy intensive and industrializing them would have been impossible without electricity
Gold is found lying around as pure metal.
Copper can be produced essentially by putting the ore in a wood fire
Iron can be produced by putting the ore in a very hot charcoal fire for a long time and controlling the ratio of fuel to air – tricky but only needs iron age technology
Aluminium requires electricity to extract it from ore (because it’s more reactive than carbon, so we can’t use carbon to remove the oxygen from aluminium oxide) so it couldn’t be produced before we had good control of electricity in the 19th century
Alum which is an aluminum compound has been used on dyes for centuries. The element itself wasn’t discovered until 1825. It is really rare to find it as an element in nature. The process to create it on an industrial scale needs a lot of electricity. So before that, it was made in small batches which made it incredibly expensive
Just a fun fact, the top of the Washington Monument is covered in aluminum because it was so valuable at the time
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