It is a cementitious lap siding (James Hardie), which has a custom alternating lap design and was painted the charcoal color. Thanks.

Is it the artisan board, or the normal lapp? I like the corner detail.

It is lap siding. Not sure what else I can add.

I was told by my contractor and Hardie's customer service that mitering the corners can only be achieved by using the Artisan line of Hardie board, and lap from the Artisan line must be used for the boards to meet at the corner. The Artisan line is a thick board and costs 40% more.

It appears that you mitered the boards for them to meet w/o using a corner board, so it had me wondering.