I would have to disagree with Bill here about using sanded chaulking between the mirror and the tile. Once sanded chaulking dries it tends to collects dust and when scrub it can discolour. I have done lots of testing with this product and prefer in the type of installation you mentioned to lap the tile over the mirror an 1/8". Great care to have full coverage up against the mirror on the edges is key so you don't view through the thickness of the glass and see voids in your setting material. I like to use Grani Rapid for this type of work because it dries nearly black in colour. Tape off the mirror with painters tape about 3 layers and under the lapped tile about 1/16" of an inch. Use care not to scratch the mirror when grouting and it's wise to use cardboard as well as painters tape to protect the mirror. Most mirrors are lightweight and can install wavy unless properly fixed to the wall. You can mount the mirror to 1/2" plywood or rig up some kind of brace to pin the mirror flat to the wall. This wall should be poker straight before you even start. Good Luck.

I did this once and put thin molding between each mirror, which gave it a french door look. I would use plywood for the backing.

Priceless picture. How large are those tile pieces? You've really peaked our interests. Huuuuuuury w/some WIPs. As CHICHEE said, we are NOT a patient group.

Look for an 80’s condo getting gutted. They are probably prying them off the wall and putting them in the dumpster. They might save you a couple if you flip them a couple of Jacksons.