The tile is called "Lithoverde" and is a natural stone comprised of 98% recycled post-industrial content.
See the September 2013 issue of Stone World magazine which features the Locust Street Bath in the article “Dream bath is also eco-friendly” , which describes the project’s modern design and use of Lithoverde. The product can be purchased through Stone Source.

The process by which this product is developed is revolutionary: Stone scraps are drylayed in layers to form a block, The block is then infused with a soy-based poly-amid binder to create a tight bond. The block can then be handled like any other block of stone; it can be sawn into slabs or tiles, or carved for multi-dimensional designs such as sinks, columns and other structures.