How do you cut combination marble and glass tiles when they are both on the same mesh backing? When I tried this, the tiles move and the glass shatters.
Ahhhhh no wet saw for small glass mosaics. First it will bounce all over when cutting and second you might get a nice chunk of glass in you.
You will be cutting everything one mosaic tile at a time. Take it off of the mesh.
#1 Make sure when laying out your tile that your cuts are in the corners or in less seen areas.
#2 If you need to cut the corner of a tile or odd shapes use glass nippers.
The nippers are not a precision tool. With a little practice you can get close to what you want. Luckily doing mosaics breaking a couple of squares is relatively cheap. If you have a weird corner cut on a tile or a circular cut and you can get it done in 2-3 tries the great job.
#3 For straight cuts you use a wheel scorer. The picture I have below is a double sided. Often you will just see a single wheel. Just like cutting drywall it is most important to get a good score on the glass side. With a little muscle you should only have to roll an area 2-3 times.
#4 Once you have a line on the top of your tile we are going to move it over to the tile cutter. You are going to place this faced up with the edge right on the cut line. This takes practice and is a little different with each cutter. You will gently (do it to hard and cut may not be clean) bounce the lever to put pressure on the tile. If it is lined up right eventually it will break clean on your scored line. If your cut isn't clean then you may need to score a little deeper or line it up better on your cutter. Also do one tile at a time. I know it seems a PITA but you can do 2-3 tiles in a minute once you get it down. Also do your cuts before you start applying thinset or have a helper.
Are you using a wet saw? I leave it on the cardboard it because it helps prevent stuff from moving around.
My trick for cutting with a wet saw is similar to using a narrow throatplate (zero clearance) on a tablesaw:
Get a smooth 12x12 tile and use it under the mosaics. Just cut it no more than 3/4 of its length, such that you keep the narrow kerf for support.
Having a smooth, continuous rim glass blade helps, also.
I used this technique to do 4ft by 4 ft by 8 ft shower enclosure of 1x1 glass mosaics. I was able to keep the sheets of mosaics intact, for the most part.
To add to DMoore's answer, cut off any full tiles you won't be using by cutting the backing with a utility knife.
Then, use the tile nippers to cut individual tiles. You'll be able to nip the tiles in half, or maybe 1/4 off if you're careful.
Then the important part comes down to planning your cuts and taking advantage of the mesh backing. Plan your cuts so they fall into an inside corner that will be covered by the adjacent tile, behind some trim, or under the faceplate for an outlet. Use the mesh backing to your advantage, shifting tiles a little further apart or closer together with a little push. By using those techniques, I avoided the need for any precision cuts on my last tile job.