Ledgestone is available with premade corner pieces that have to be used for this installation.

However, ledgestone popularity peaked about 5 years ago, so I'd recommend you consider a different material.

Fireplaces are architectural elements in the home and should complement the architecture of the house IMO. If the house is traditional, then continue that style with the fireplace.

If it's contemporary or modern then continue that style for the fireplace.

Not personally a big fan of the premade corner pieces for this type of stone, they accentuate the fact that it's prefabricated material and does not look professionally finished. With the proper saw you could cut the sheets, then miter them to create matching pieces that wrap the corners. You may have to lightly grind the miters and fill the gaps with grout to achieve a more seamless joint. I personally would have to throw in my DIY towel and hire someone with a higher level of skill to do it that way.

IMO ledger stone is dated and never reallymeant for interiors. Why not look at some nice large format tile in a color you like use a nice simple schluter to do the corners where it is alnmost invisble and gives a nice clean edge . I aslo think keeping those stones clean will be a puzzle .

that looks nice. I was going to say they make corner pieces but your tile guy figured it out

Very nice!