French_Fried said:
Why are glass coffee mugs so rare

Glass doesn't last much long when it takes on a lot of heat either.

@KynikossDragonn: like when I used a clear glass salad plate in the microwave. After a while of use (years), it just breaks.

KynikossDragonn said:
Glass doesn't last much long when it takes on a lot of heat either.

Pyrex (low-thermal-expansion glass, often has a brown tint) is designed for the microwave and seems to last well.
I haven't seen it in mug form, but I'm not actually looking for a glass mug myself, so..