AMS Landscape Design Studios, Inc. This is a Quartzite stone called 'Woodbridge' from a company called Walker Zanger.
It is extremely durable and does not have any issues similar to other stone, like slate or travertine. It does not need to be sealed either.
This pattern is their 'Ashlar' or 'Versailles' style.
There is perhaps no greater way to terminate an axis than at an outdoor fireplace. The symmetry is further reinforced with twin urns and twin sofas, and even the tall trees beyond are nearly twins. The exterior walls here are softened by lush plantings and ground cover. A stepped perimeter curb sets apart the perfectly flat stone paved terrace. A space like this is designed for retreat and respite from the outside world, and all major spaces of the home have access to it.