Re: Cutting Glass Block
First this warning from Pittsburgh Corning-
"Can glass block be cut?
This is NOT recommended. Because of the partial vacuum in the block any drilling or sawing could cause the block to implode. Also an installed cut glass block will eventually form condensation, mold or mildew on the inside. Projects should be planned so that only whole glass block units are used. "
When I need to drill a hole in glass I use a diamond bit, continuously let water flow on the bit, and apply very little pressure. I have never cut glass blocks but you may be able to do it with a wet diamond saw. You can usually rent them at tool rentals. Wear heavy gloves, a welding apron if available and full face protection. Don't rush it. One wrong move and the glass can explode.
Be sure you live your life, because you are a long time dead.-Scottish Proverb