Not-so-precious metals: tools with only precious metals are available

Question

Imagine a world where only precious metals are available. They are as common and plentiful as iron or aluminum are in our world. Any metal that is not precious does not exist outside of biological forms, like the iron in our blood.

Taking this into account, which metals, or alloys, would be the most used for tools? Things like axe heads, pickaxes, knives, etc.

For the purpose of this question, let's use the wikipedia's list of precious metals: https://en.wikipedia.org/wiki/Precious_metal#Rough_world_market_price_($/kg)

Answer 1

Palladium White Gold

Jewelers have spent centuries learning to alloy precious metals in ways that make them strong enough that they can include tiny details without being too delicate.

While pure golds (24k) are soft and delicate, but golds between 14k and 18k are a lot tougher than most people give them credit for. Cast gold is usually used in jewelry making meaning that lower karots are often needed to get desired hardness and toughness, but like bronze, these are typically work hardened alloys. If you were to cast a typical 18k gold, and hammer it into a blade or armor, the resulting alloy would have a hardness and tensile strength slightly better than a 1055 rolled medium carbon steel.

The ideal gold alloy for this is a mixture of about 75% gold, 20.5% copper, and 4.5% silver. Unfortunately, Copper is not on the list given by the OP (despite being on many other precious metal lists); so, we need to look to other gold alloys with similar properties if we want to meet the OPs specs as asked.

This is where the palladium comes in. Palladium is sometimes used to substitute for copper or nickel in gold alloys because it gives a similar hardening factor when caste while also being hypoalergenic... but unfortunately, it does not work harden like copper gold alloys. Instead jewelers add Ruthenium to Palladium Gold alloys until it reaches its desired hardness. This alloy wont be quite as durable as a work hardened copper-gold alloy, but it can get pretty close. The resulting alloy should be about 60% gold, 15-20% silver, 15-20% palladium, and 5% ruthenium, and you will be suitable for a wide range of tools using only the elements on the OP's list

Ultimately, the resulting alloy will be just as tough as a lot of the weapons and tools made throughout most of the iron age, but the metal will be more dense and heavy. So, you will likely see a lot of shorter weapons and tools. A gold alloy gladius or kopis might work even better than early steels because the higher density will give you more power without broadening the blade profile, but don't expect any long swords or full plate armor since the increased density would make those prohibitively cumbersome.

Answer 2

Beryllium, all over the place...

Beryllium is not even remotely related to what most people consider to be a precious metal, but it’s on some lists of precious metals (including the one the question states to use as a source) for two major reasons:

• It’s comparatively rather rare. Not as much as the platinum group metals or gold, but enough that it’s abundance within the earth’s crust is best measured in parts per million.
• It’s absurdly useful stuff.

Beryllium is actually a surprisingly good structural material. It has a rather low Poisson ratio, a bulk modulus not much lower than steel, a shear modulus and Young's modulus much higher than steel, and a lower coefficient of thermal expansion than steel. It’s also reasonably hard without being too hard to be useful, and has an absurdly low density for a metal (1.85 g/cm³, compared to 1 g/cm³ for water and about 7.85 g/cm³ for typical steels).

Of the metals on the list being used here, beryllium is the single most useful option, and it will be used almost everywhere.

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Other things to note:

• Hammers and other things that need to be heavy will probably use platinum or a platinum-iridium alloy.
• Osmium-iridium alloys are likely to be used for things where weight is negligible or does not matter, but durability is super important. They even beat out tungsten by some measures of durability.
• There will be no real replacement for applications we currently need super-hard materials like tungsten carbide for. You simply cannot get to that point using just the metals on the list.
• Copper is going to be super valuable here for a number of reasons.

Answer 3

Eternal Stone Age or Advanced Space Age

None of those metals on their own are particularly good for use as large tools. Gold doesn't make a very good axe and silver doesn't make a very good weed whacker blade. So, absent any kind of cool alchemy, people would most likely continue on with tools fashioned from stone, wood, laminates, bone, etc. Small tools, like surgical instruments, spectacle frames, weights, food vessels and so forth are all viable contenders for being made from almost any precious metal. (Would stay away from gallium dinner plates, though!)

However, if you allow for curious alchemies, there are alloys of precious metals that could prove to be viable in tool making. One could argue, perhaps, that the concept of mithril, hard as steel, lustrous as silver, is just such an alloy.

Answer 4

If Iron is available in biological forms, it could make for quite grim stories of harvesting it.

There might be ceramics (you might want to avoid the most obvious one, BeO, due to its horrible toxicity...) and amalgams based on only precious metals not known to our science because nobody looked hard enough, for lack of a practical application.

And do not underestimate good old carbon... as diamond, or carbon nanotubes, it could be useful in quite many tool applications.

Answer 5

While a world that follows the premise of the question has serious issues to face, just going along with it, I think you might find this wiki page helpful.

Hardnesses of the Elements (data page)

In such a world there would be alloys that we've never even thought of trying to make, and they would likely find some alloy that solved their problems. However, if we're sticking with pure elements, of particular note is rhodium, the first element on your list of precious metals, which has a Brinell hardness of 540, comparable to abrasion resistant steels used in the mining industry and much harder than things like cast iron or even tool steel. It is also durable, so it doesn't wear easily. It's a noble metal, and like all of that family is is very non-reactive.

It's not perfect, of course. Its biggest drawbacks are that it is brittle and that it has a high melting point.

I don't know if anyone has ever simultaneously possessed enough rhodium and had the desire to make a hammer or axe head out of it. In its pure form it can't be made into good jewelry because it's tool brittle and the jewelry breaks. That said, a large lump of it is a different question, and it would definitely be possible to chop down a tree with an axe with a rhodium head. Breaking rocks? The pick/hammer might shatter or chip, depending on the hardness of the rock. However, again, it should be comparable to AR steels, and they're used for mining purposes.

It melts at 1538°C (3565°F). This is above the temperature that a coal/air forge can reach, so it couldn't be cast using coal to melt it. To be clear, it would be able to be heated to workability in such, and since it is typically found as an uncombined metal (like gold, basically) it should be able to be forged into a lump and then further into whatever shape is needed. It is apparently quite difficult to machine - there are numerous machinists complaining about it ruining their tooling on forums.

Neither better nor worse really, but worth considering, is that it is also ~1.5 times denser than iron, so any tools would be heavier (or smaller).

Finally, if weapons are a consideration, it would be fairly awful for most of them. It would potentially make a ferocious projectile weapon (arrowhead or bullet, that is) but a large, chunky sword or axe would be too heavy for human scale muscles to use effectively and a thinner weapon would be too easy to shatter. I guess that might actually pose an interesting challenge to duelists - not quite as bad as fighting with glass swords, but a similar idea.