[chimeracoder]

Since when is glass (I assume we mean soda-lime glass) a separate phase of matter?

My impression was that it was a solid, and that the myth that it's a highly viscous liquid was based off of incorrect analysis of stained glass windows, etc. that were more likely explained by imperfections in the production process.

[ajross]

"Phases" are poorly defined. They exist wherever there's a statistical mechanics reason to define them, and they make sense only within the limits of the approximations on which they are based. Glass is "solid" to a mechanical engineer (in most regimes), but it's not a crystal and doesn't behave like one to a solid state physicist. Likewise "plasma" is a great tool to describe a fluorescent light bulb or lightning bolt, but not so much a white dwarf. Even stuff you think you understand, like "liquid and gas are clearly different" turns out to be wrong (http://en.wikipedia.org/wiki/Supercritical_fluid).

[stephengillie]

My impression was also incorrect. Wiki says it's an "amorphous solid" aka one that doesn't form into crystals.

https://en.wikipedia.org/wiki/Glass

There's also Amorphous Ice, which is arranged in a "glass-like" form: https://en.wikipedia.org/wiki/Amorphous_ice