What is the strongest glass that can be formed from nature?

Question

tl;dr What is the strongest glass that can be concocted from a single reasonably abundant, natural source? (Without nuclear or quantum manufacturing)

So I am developing a character for a story. He has powers that are very similar to alchemy in Full Metal Alchemist and in FMA they have the Law of Equivalent Exchange which states:

Humankind cannot gain anything without first giving something in return. To obtain, something of equal value must be lost.

So basically he uses magic to make a thing from other things. On the atomic level (let's not be cute and bring quantum mechanics into this. He transforms elements.)

Also, he can't guarantee a crystalline shape due to failing geometry and geology (no diamond cuteness). His life is a mess but he does not apologize. Failing chemistry is why he can't just whip up an explodey or a chemical weapon.

But that's all fine with him. He can just make hard stabby things appear from the nature, preying on the fear that living things have of being stabbed. So basically he is creating glass (this includes metallic glass).

So my question: what is the strongest glass he can make strictly from commonly occurring natural surroundings?

Key points I will use to judge an answer:

• It shouldn't be crystalline. I am looking for a glass, e.g. a non-crystalline amorphous solid
• It doesn't require anything man made. Pretend the world is a wonderland untouched by man.
• It doesn't require anything living. PETA, TreeTA, and PeoTA really screwed up this guy's life. He doesn't need another lawsuit. Dead is fine though.
• It doesn't require carbon. This is a bonus, but I like it because some people don't count trees and bacteria and mollusks as people. But a lawsuit from BacteTA sealed that deal.
• It's transparent. This is also a bonus, but if a person makes a shield, it helps if they can see through it.
• It is fine if any carbon or living organism get caught up in the creation, they just can't be ingredients in the creation.

Answer 1

There is a common misconception about the difference between tough and hard. Tough materials can take a lot of stress without breaking. Hard means the material is hard to indent. So I wonder: Drop a ruby (hard) from a tall building. Will it be scratched? No. But will it shatter? Probably. Even worse, there are math equations that show that a material can’t be insanely hard and tough at the same time. So I tried to find a glass that was at least somewhat hard and somewhat strong. I present:

http://www.pnas.org/content/105/51/20136.short

Titanium BMG

This glass uses titanium (famous for hardness) and zirconium in glass to produce a glass harder than steel and more importantly tougher. If you are going against flesh then I’d suggest something with more hardness and less toughness, but any kinda armor and your glass or corundum spear will shatter. Try this one instead!

Answer 2

what is the strongest glass he can make strictly from commonly occurring natural surroundings?

While not crystalline, glass still is made up of a ionic lattice; it's simply highly irregular and nonrepeating.

What you want to obtain is strength, i.e. resistance to fracture. This can be obtained by having the ionic latticework subjected to a really strong compressive tension, so that a fracture would have little to no chance to form.

One way of doing this is to heat the glass at a precise temperature range, then suddenly cool it so that the outside shrinks at a different rate from the inside, giving rise to large residual stress. To break the glass, you first need to overcome that stress; this is how Batavian tears (aka Prince Rupert's Drops) can withstand the impact of a bullet.

Another way is to force the lattice out of its natural shape; this is still a poorly exploited branch of chemistry, but it gives origin to things that explode more than they should (octanitrocubane), springs that are more elastic than they ought to be, and glass that it's way stronger than it had any right to be.

The lattice stretching process is usually performed by replacing atoms and groups with other atoms and groups that are compatible, but much smaller, or larger, than the ones they replace. Replacing sodium with potassium gets you Gorilla glass; replacing it with other metals gives you "transparent aluminum" (not real aluminum, Mr. Scott, I know!) and other high-tensile strength glasses.

I have read that Gorilla glass is about 20-30% of the maximum theoretical stress that the lattice can withstand (i.e., if you made it ten times stronger, it would explode by itself). This is using normal soda aluminosilicate glass to start with, which I think is your case - otherwise you'd have some other ceramic.

So, I think that a strength three to four times that of Gorilla glass is achievable if you have a fine enough control on matter.

Answer 3

Silicon Carbide is pretty amazing

This is also known as Moissanite (SiC) . It's almost as hard as diamond. Color varies but is generally transparent.

If the absence of carbon is a hard requirement then corundum ($Al_2O_3$) would work too. Generally transparent except when contaminated with impurities. When contaminated with chromium, corundum goes red to form ruby. Corundum is just behind diamond on the Mohs Hardness scale.

As long as these are stabbing only weapons, then Moissanite and Corundum should do nicely. If none of these are acceptable, further reading can be done on hardest crystals. Remember, the only difference between boring mundane graphite and a diamond is how the crystal is shaped.

Silicon, carbon, boron, oxygen and nitrogen are all very common elements. Forming into the right crystals is what makes them mind boggling strong. Most every rock you see is made of silicon and oxygen. You'd be very hard pressed to run out of raw materials.