You can use a diamond blade suitable for glass, the finer the better (I use a Bisazza blade). If possible use a variable speed grinder or a cordless one, because the lesser speed of those grinders dont put as much pressure on the glass. Hold the mosaics in place with a grout float in case you slip.
Dont try and cut them in one go as theyre more likely to shatter. Run over them initially making a grove for a guide and then gradually work through them.
scribe and snap is fairly easy, use this tool to scribe a row, guide it against a ruler to make it a straight line, then sandwhich one side of the mosaic between two blocks(scribed surface facing up), push down on the otherside and it snaps cleanly down the scribe. You may need to run a knife through the mesh still
[video=youtube;A4Z3WTHQXw8]http://www.youtube.com/watch?v=A4Z3WTHQXw8&feature=context&context=C33175 36ADOEgsToPDskJiyAwR4c07gckNj1BCGpvi[/video] a rubi will also do the job 😛rrr:
i've been using my mini sigma for cutting mosaics on my latest job and to my surprise it does them with ease. i seen a demo on a montolit (with the rubber mat) a few years ago and that looked good too. i usually use a good glass blade on my grinder though.