Porcelain tile, probably 6" x 18". Take the photo to a good tile store and they will probably have something similar.

Looks like wood grain porcelain tile, like this.

And just for fun, it could be a marble-mimic porcelain tile....or a travertine or travertine look tile.

So...to narrow this down, it could be:

1. Porcelain tile

2. Marble

3. Travertine

4. Porcelain tile that looks like one of the above

Fun isn't it?

Go for the colour in the pic. If you can find movement like that, then good for you! If not, you will still have the "look" (look often comes from colour...).