[benj111]

I'm not sure of the correct scientific language here.

As far as I'm aware this is a brittle /inflexible material so my point about the mechanical properties still stands.

And when people refer to growing crystals, that generally refers to a particular kind of crystal. Ive never heard of anyone growing aluminium crystals, except if it's a compound, and then you get a crystal like we think of when we say crystals.

[kergonath]

> As far as I'm aware this is a brittle /inflexible material so my point about the mechanical properties still stands.

Yes. You want them to be ductile (malleable, or that can be deformed permanently in less-technical language). Although they could also be flexible (meaning that they can deform, but go back to their natural shape if we stop applying a force), as in the case of fibre optics cables, which are actually not crystals but quite brittle.

The interesting twist is that a solid pretty much has to be a crystal to be malleable. Almost all the metals you can think of are in their crystalline state.

> And when people refer to growing crystals, that generally refers to a particular kind of crystal.

I don’t know. From my experience people equate crystals with shiny things without really thinking about it. But this is HN, and we should try to be a bit better than a random person on the street. After all, most people don’t know a web browser from an OS, but I would be ridiculed if I make that confusion here.

It is a wonderful community where you are almost certain to discuss with some experts in pretty much any given field, it is a great opportunity to learn and grow.

> Ive never heard of anyone growing aluminium crystals

If you’ve seen solid aluminium, then you’ve seen it as a crystal. It is pretty much impossible with common techniques to get non-crystalline solid aluminium.

> except if it's a compound, and then you get a crystal like we think of when we say crystals.

That’s the thing, I don’t know what you think of when you say “crystal”. In actual fact, a crystal is a state of condensed matter in which atoms or ions are aligned in a 3-dimensional pattern that can be replicated to fill the space. In the case of aluminium, you can actually see how the atoms are arranged in a periodic way in articles such as this one (figure 3): https://www.researchgate.net/publication/323423565_Anomalous... . There are many other examples, and it is absolutely fascinating. We have the tools to count atoms and see the structure of the material!

And it is undoubtedly a crystal.

[benj111]

Ok so what is the terminology to refer to this class of materials?

A ceramic?

I'm happy to accept that internet explorer isn't an OS, but it would be nice to know what terminology you would find acceptable.

[kergonath]

I am not the one deciding on terminology. In this case, both copper and aluminium are crystalline metals. Any lump of these is actually formed of a lot of smaller crystals bunched up together in what we call polycrystals. This is why they don't have the nice geometrical shapes people tend to associate with crystals in pop culture. But depending on how the material was made, these geometrical features can be seen with a magnifier or a microscope.

I am not blaming you, I know the knowledge of the general population of this sort of things is not great and you cannot know it before some tells you. A whole bunch of new age scams would completely fall apart if most people actually knew what a crystal is and where we can find them.

They are not ceramics because this is used for compounds with elements such as oxygen or nitrogen, which is not applicable here. Aluminium oxide, Al2O3, which used in sapphire "glass" in watches, is a ceramic that contains aluminium.

[kerkeslager]

> I am not the one deciding on terminology.

No, you're just the one pedantically enforcing a definition that's irrelevant to the conversation at large.

You aren't holding up your end of the conversation. Being a good listener means putting some effort into understanding what people are trying to say even if they get terminology a bit wrong. Jumping in to correct people on minor misuses of terminology doesn't show you're smart, it shows that you care more about correcting them than about their ideas.

I mean, cool, good to know copper and aluminum are crystalline metals, but the point here is that they're ductile and LK-99 isn't--you can't make wires out of LK-99. Arguing that copper and aluminum are crystals isn't adding to the conversation, it's just missing the point.

[kergonath]

Ok, I doubt anyone is still reading this, but anyway…

> No, you're just the one pedantically enforcing a definition that's irrelevant to the conversation at large.

I am not enforcing anything. How could I, anyway? I am pointing out an error in terminology. It is far from irrelevant, all the threads about that subject are full of misinterpretations and misunderstandings. One of the reason for that is that scientific articles use the jargon of the field, which can deviate from how certain words are used in our daily lives.

> You aren't holding up your end of the conversation. Being a good listener means putting some effort into understanding what people are trying to say even if they get terminology a bit wrong. Jumping in to correct people on minor misuses of terminology doesn't show you're smart, it shows that you care more about correcting them than about their ideas.

It is not a small vocabulary issue. This stuff is fundamental materials science and you cannot understand anything about this subject if you are confused about this. Again, this thread is full of people who are confused because they don’t understand some words in the same way as the writer. Crystalline and amorphous materials have very different properties as far as conductivity is concerned. The crystalline aspect is fundamental.

> I mean, cool, good to know copper and aluminum are crystalline metals, but the point here is that they're ductile and LK-99 isn't--you can't make wires out of LK-99. Arguing that copper and aluminum are crystals isn't adding to the conversation, it's just missing the point.

What is missing the point is that we know how to make wires with brittle materials. Prime examples are silica in fibre optics and YBCO in superconducting tape. And yes, whether they are crystalline or not is very important for both of them.