What size ropes are you all using glacier travel with large (3+) rope teams? 9mm or smaller? I often take friends out to climb some volcanoes and have used just what I have around but now im looking at buying a glacier specific rope and wondering what size is standard in the "industry."
I'm usually fine using a half rope for even large glacier rope teams. Fall forces are so low compared to, let's say, a FF 1.77 drop that these ropes are tested on by the UIAA, and falls seem less likely than on rock. I use the 8mm Mammut Phoenix. Half ropes are less resistant to cutting, though, so taking extra care to avoid stepping on the rope or chopping it in any way is probably a good plan.
Edit: I didn't see that you said "Hey guides", I'm not a guide but that's what I use for personal trips. I'm sure there's a guiding industry standard, and it probably includes pretty burly ropes if I had to guess.