You’re going to get grout lines. Grout is required for tile installations. The edges can be mitered, but that requires a tiler with a higher skill set. Fake marble is cheap and tacky looking. Real marble is porous, and will stain and etch.

This isn’t a cheap project at all. It’s going to have a certain base cost to do, whether the majority of costs is in the material or the labor. 5K is on the very low side to this. Doing one right now in limestone that’s 30K. It stains and etches too. They’ll just replace it again if that happens.

Not sure what kind of look you are going for, but we did 10x60 tiles with mitered corners and it turned out great - we did use Schluter on the finished edge that was not in the corner. Does your fireplace box NEED to be 7' wide?

That looks fantastic. Unfortunately I designed the fireplace box and it’s already dry walled in. Which Schluter did you use? It doesn’t look too noticeable.

Macdolen- I think the fake marble might have looked cheap in the end. That was my fear. I’m glad you said that.

We did not use schluter on the corners. they very carefully miter cut the tile. We used a brushed nickel a schluter on the end that finishes at the wall. An 8’ tile is going to be hard to come by.

First off no sheetrock on a fireplace its not fire rated.

You can easily miter the corners but the walls require the right amount of prep. If your corners are not sharp 90's your tiles wont be either. Schluter is not needed anywhere on that project.

As far as slab you can look into using prefabbed counter slabs as they are cheaper than full slabs. We did an entire prefabbed marble look slab shower installed for under $3500 and it looks amazing. Couldn't touch that withal slabs.

Also Porclainosa sells thins slabs tan are approx 3/16 thick that ae also are cost effective. Actually on the lower end Floor and Decor is also selling a thin LFT that could also be utilized.

Thin slabs are big in Europe as they don't believe in waste like we do and tiling on top of tile is more common place.