Glass and Mirrors - cutting wall mounted mirror

I have a morror mounted to a wall with adhisive that is about 1" too long for the new vanity top I am putting in. I have been trying to cut it (scoring it with a window cutter) but cannot chip it off. Any suggestions? If I crack the mirror...oh well. But would like to avoid that.
Paul

If you are trying to cut it while it's on the wall.....forget it. If you removed the mirror and you scored it with the glass cutter and you were unable to remove the 1" piece it's too late now. You can only score it once and break-out the cut immediately. It's not easy to remove a 1" piece without a glass plier or experience. I suggest you practice on some scrap glass and then you must make a new cut and remove at least 1 1/4" from your mirror.

Shouldn't cost too much to have a glass shop cut it to size for you.