Crystal sword...

[starslayer]

Fiberglass is pretty resilient material, and there are several varieties that are actually transparent (Fiberglass in this context being the generic term, so 'fibrous strong fragile material suspended in matrix of soft flexible material')

It might be possible to use something like diamond slivers or carbon nanotubes in an already strong poly-carbonate matrix to make something that would be serviciable as a blade (but still inferior to an actual metal blade).

This article is rather well researched even if its about apple, with links to multiple researchers and various projects
https://www.compositesworld.com/blog...ent-composites

[Fred Brackin]

Originally Posted by Paulon

Frostreavers. They melt when they get above the freezing point.

Those were axes rather than swords.

[Flyndaran]

My first thought was, "does that matter?". But then I supposed that axes probably don't need the flexibility swords do, so stiffer materials may work for them anyway.

[Anthony]

Originally Posted by Flyndaran

My first thought was, "does that matter?". But then I supposed that axes probably don't need the flexibility swords do, so stiffer materials may work for them anyway.

Material requirements for axes are generally less challenging than for swords. There's a reason you can find stone axes but can't find stone swords (unless you count a Macuahuitl).

[lwcamp]

Originally Posted by mhd

And to match the fantasy cliche, it pretty much would have to be a single crystal, wouldn't it? With no boundaries to mess up refraction.

Or it could have cubic crystal symmetry. Cubic symmetry crystals are isotropic, so that the boundary between two crystals will still have the same optical properties on both sides and thus will not scatter light. You can get transparent polycrystalline materials if the atoms align on a cubic lattice.

Luke

[Anthony]

Originally Posted by lwcamp

Or it could have cubic crystal symmetry.

Or it could be an amorphous solid, such as glass, that's cut in whatever shape desired.

[starslayer]

Are there any crystals/glasses that have the same refraction index as air?

That would actually be kind of neat. (though would have virtually nothing to contribute to a crystal sword because its physical properties would likely be junk, but it would be neat because it would be virtually invisible).

[Anaraxes]

Originally Posted by starslayer

Are there any crystals/glasses that have the same refraction index as air?

The best I found with a quick search was a TiO2-SiO2 material intended for making graded, anti-reflective coatings to gradually match the substrate index with that of air, which material could be adjusted down to about 1.05. So by that metric, the glass sword is looking better (ha) than the ice one -- though the paper didn't cover the material properties or behavior in larger than tiny surface applications.

Feel free to substitute sufficiently advanced magic for the self-shadowing thin-film vapor deposition nanotechnology used in the paper.

[Flyndaran]

I wonder if anyone's created a setting on a frigid world, possibly with liquid ammonia, where ice is the stone-like material for making weapons.

[GodBeastX]

Are we talking JRPG fantasy trope? Because crystal in JRPG tends to be "Solidified Mana". And who knows what properties that has. Create your own! Could even do bonus magical damage like Azzalum from Fantasy Tech 1.

If it's "glass", then just use Superfine weapons from Ultratech which would include "Ceramics".