I'm noticing a very nice detail that shouldn't be overlooked. On the edge or corner detail where one tile meets with another, typically overlapping the tile or using a Schluter' "joly" to finishing the corner edge would be used. But here I believe you've mitered each tile so they meet up perfectly. Nice clean job by the way.

Have you done this with other tile like ceramic or just natural stone tile. I'm finding it hard to even find an installer to even attempt this for me.