Green? The OP said mitered edge. Why does it have to be 2.5" or more? She has the plywood support and the thickness of the granite but why quite that thick?

My fabricator was going to do a 1.25" mitered edge on Ceaserstone. I actually switched to Cambria and have a 1.75" mitered edge instead. Looks fabulous!

I have a mitered edge on one bathroom vanity (2 cm Ceasarstone Organic White). I'll measure it when I get home, but I'm fairly certain it isn't 2.5".

"My countertop fabricator is saying he can only do a 2.5" mitered edge or thicker."

This is probably a machine and/or tool problem on his end. He probably doesn't have any pods small enough to hold the pieces and isn't low-tech enough to do it by hand.

A miter can be any depth.

Make sure your fabricator is going to do a mitered edge versus a laminated (stacked) edge. A mitered edge is much more difficult to do & some fabricators just don't have the skill level to do mitered edge that has an invisible, non-chippy seam where A meets B. I'd ask your fabricator to make a sample of the stone edge

This is a mitered edge:

This is a good mitered edge:

This is a not so good mitered edge:

This is a laminated edge. The stone is stacked with a seam between the two pieces of stone. The first one doesn't look too bad. We've had some unhappy people post laminated edges that have either had a very visible seam between the two pieces of stone or the pattern/color of the top piece of stone is an obvious mismatch to the bottom piece of stone.

In the countertop world, we never use the word "invisible". It's always "inconspicuous". I'm not playing semantics, I'm setting customer expectations. You may get invisible, but a respectable fabricator never makes that promise.

This is a beautiful miter on a Chinese estone blank at a local tile store.

The "movement" and "particulates" in the material play a major role in mitering vs. stacking edges too. A machined stacked edge on a fine particulate with little movement will look even better than a miter because the seam is further from your eye.

Joseph - you are right. When I typed "invisible," I knew it wasn't the right word. My seams aren't invisible, they are inconspicuous. We have had several GWer's, that requested a built up edge, assumed it was a mitered edge, & were unhappy when it was a conspicuous laminated edge. Linelle's countertops are an example of an inconspicuous laminated edge.

Here is the mitered edge on one of my Ceasarstone counters. It's 1.75".