I've been wondering about this for ages but haven't been able to find anything at all. Anyone know?

Just taking a stab in the dark here.....but wouldnt it be because of the silica/silicon dioxide? Since silica is inert, wouldnt that in theory prevent it from reacting with the chemicals in the beaker, etc?

http://en.wikipedia.org/wiki/Silica#Chemistry

It react's with hydrofluoric acid, hot alkali(base), etc, but i guess thats why they use different materials in it to help reduce it.

Maybe someone else has something more to add...

It's inert cause they make glassware out of it and they make glassware out of it cause it's so inert

In highschool i think they taught us how to answer this right after we discovered what the groups in the periodic table are for.

I wasn't paying much attention at the time, there was a few babes in my class which proved very distracting.:p

This depends on how much into detail you want to go. glass is silicates, and although there is no long term order in the structure, they tend to have a a-quartz short term arrangement. silicates are clearly very stable (indicated simply because there is so much in nature, the same reason you don't find sodium or potassium metal in nature).

the reason why silicates are (or why one thing is more stable than another) stable is fairly complicated. there are theories (like hard/soft-acid/base) that allow you to guess quickly, but most don't really apply to covalent bonds. you would have to go into some quantum mechanics to really get a decent answer. it's just one of those things, carbon likes to bond with hydrogen, silicon likes to bond with oxygen. i'm afraid i can't do much better than that.

if anyone has a better answer i would love to hear it, this has got me curious.

In highschool i think they taught us how to answer this right after we discovered what the groups in the periodic table are for.

This. It's because of the valence electrons, if an atoms outer shell is full it is less likely to react.

thats a massive over simplification and mostly wrong. almost all molecules encountered have full valence shells, yet exhibit massive differences in stability.

carbon oxides form silicate like structures, but are unstable at pressures below about 10 GPa. carbon oxides and silicates have the exact same electronic structure (carbon and silicon are in the same group) but form solids with radically different chemistry.

This. It's because of the valence electrons, if an atoms outer shell is full it is less likely to react.

RAOVQ pointed out a good example of how this doesn't apply to molecules.