The options for bathroom flooring can seem endless, but for a flooring design described by the World Floor Covering Association as "timeless" and "practical," some homeowners choose natural stone tile . Stone provides the kitchen & bathroom with a rustic look that is durable and relatively low maintenance. Theses are heavy and difficult to install yourself, but with adequate planning and patience you can transform the look of your bathroom. 
Instructions as follows:
Firstly, clean your subfloor to remove all contaminants. Sweep or vacuum, then clean the surface with mineral spirits or a similar solvent cleaner to remove any wax, grease, paint or other buildup. Allow the floor to dry completely before continuing.
Secondly, measure to the center of each stone wall and make a mark. Snap a chalk line between the center points of opposite walls, creating a plus sign on your floor. The point at which these two lines cross is the center of your room.
Thirdly, lay out your tiles without any adhesive. Start at the center point of your room and lay tile in one corner. Lay along the center lines and fill in the center, until you lay as many full tiles as you can. If necessary, use spacers to maintain an even joint between tiles.
Fourthly, measure the tiles you need to cut for border tiles. Lay the tile against the wall face-down. Draw a pencil line on the back of the tile where it intersects the nearest full marble tiles. Be sure to include joint space in this measurement. Repeat with all border tiles.
Fifthly, wear protective gloves and goggles when cutting tile. Use a 10-inch diamond blade on a wet saw to cut along your marked lines. When the tile is cut, use a handheld whet stone to smooth the cutting edges, eliminating sharp points.
Sixthly, check the fit of all of the cut stones and make any adjustments as necessary. Remove all dry laid tiles once you have the final pattern fit.
Seventhly, mix thinset tile mortar and additives as instructed per product specifications. Use a notched trowel to spread a layer of thinset across an area five to six feet in front of you.

Eighthly, using the trowel, spread a layer of thinset onto the back of each tile, then press it firmly into the thinset on the floor. The thinset will bind together, holding the sandstone firmly in place. Continue to install, adding more thinset to the floor as necessary.

ref.:www.stonebtb.com