The floor is a Calcatta Marble. It can be purchased from Joanne Hudson Tile & Stone. More information about this company can be found at: http://www.joannehudson.com/tile-stone
Hello! In case you still need help, here is another photo of that floor tile in another installation. You could purchase it through this website - http://www.architecturalceramics.com/portfolio/357-arabella-bathroom-with-gibson-builders
Kass & Associates
Casey Terrell/Architectural Ceramics