Comments by "EebstertheGreat" (@EebstertheGreat) on "The Most Important Material Ever Made" video.

Technically, a glassy phase of carbon exists (AM-III) which is harder than natural diamond, i.e. above a 10. It's opaque, though.
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@lord_woodhaven6426 Apparently there is a youtube channel called JerryRigEverything which among other things tests phones, including testing the integrity of their screens. He uses a Mohs hardness kit to measure their scratch hardness, and basically every phone screen will get slight scratches with the #6 bit (made of orthoclase feldspar) and deep grooves with the #7 bit (made of quartz). And I think "glass is glass, and glass breaks" is something he says a lot on the channel.
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@kazedcat I didn't say anything about toughness or breaking. I specifically said it was harder than natural diamond. So it won't scratch at a 6 or 7 or even a 10.
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@kazedcat Tungesten carbide is not glass. I was responding to the OP. Like how threads work. I don't get your confusion. Also, tungsten carbide has a Mohs hardness of 9.
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@kazedcat It is a glass though. It's formed by melting and quenching to prevent crystallization, resulting in a hard amorphous solid. Just like silica glass or obsidian. Polyacrylate can form a glass too. But more likely you are thinking of poly(methyl 2-methylpropenoate), aka Plexiglass, Lucite, or Perspex. That is also often called glass, as it fits the technical definition, but some people exclude polymers from what they call "glass." AM-III carbon is the hardest glass.
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@kazedcat All glasses are amorphous. But "acrylic" is a vague enough term that it could also refer to a crystalline solid (e.g. you can find X-ray crystallographic studies of polyacrylate). But yeah, the kinds of acrylic you normally come across are technically glass, in the sense that they are in an amorphous solid phase that can transition to a viscous liquid by heating above the glass transition temperature.
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@kazedcat I wouldn't say that every amorphous solid is a glass, but physically-speaking, yes, plastic bottles are generally glassy in the sense that they have a defined glass transition temperature above which they form a vitreous phase and below which they form a glassy phase. There is of course more than one meaning of "glass." Some people use it exclusively for solid transparent silica glass, so for instance obsidian would not be called "glass." But clearly that's not the meaning used in this video. AM-III is every bit as much glass as obsidian. Some people use the definition I've been using but specifically exclude polymers, like I said. In that case, AM-III would be glass but plastic and amorphous polyacrylate would not. That's kind of the "nuts aren't fruit" version of the definition, excluding some specific things cause they don't feel right. But even then, AM-III would still qualify.
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