Pure ammonia is "supposed" to dissolve silicone.
I just did a significant job that required removing silicone and used a LOT of it. I think my razor blade was the only thing that "softened" the silicone. Wet silicone is most defiantly dissolved by ammonia, but I have my doubts about cured silicone.
Before you start this task, ask your self..... are you sure you will ever use this glass or are you stashing things away because you can? Ever needed a piece of glass before? Its probably not tempered either, and you can buy that glass at Home Depot/Ace/True Value for a few $$ if you ever did need it. I really doubt its worth the work unless you have a specific project in mind. And even then, I would consider buying before I took that apart.