We often get asked this question so I thought I’d post some advice to the solution. Most natural stone tiles have "sawn" edges also known as "rectified" as they are dead square. Marble tiles in particular can also come with slightly bevelled edges as well which can complicate this issue slightly. When you've got a window to tile around, or the inside of the window, also known as a "reveal" you will have two tiles that butt up against each other at 90 degrees. You will see the edge of one of the tiles. We recommend that you don’t butt the tiles up against each other but leave the width of your grout joint between the two. If you’re fortunate enough to have a factory finished edge exposed then you have a few choices as to how to finish this edge off to give the best aesthetic look. One thing you really don’t want are "tile trims". Avoid these at all costs. There is no place for plastic tile trims in your beautifully marble tiled bathroom.
Polished marble tiles and polished limestone tiles can be polished in-situ. What we recommend is that once the tiles are installed that you either leave the open edge "raw" i.e. in its unfinished state. This might sound unsightly but it really does look ok. Alternatively you (or more likely your installer) can go to the trouble of polishing the open edges with some rubbing compound and a polishing pad on low speed polishing machine. This won’t give you a high polish but will make the edges look practically like the surface of the tiles. If you have an exposed edge that has been cut by your installer then we recommend that it is tidied up with wet and dry paper as detailed below before polishing takes place.
The edges of honed marble tiles and honed limestone tiles don’t need any polishing as such unless you have an edge exposed that has been cut by the installer. In this instance you can use a fine file to take out the cutting machine marks or use some wet and dry paper with a sanding block and rub the edges up and down until they are perfectly smooth. A bit of effort required here but well worth it. You will find that the factory finished edges on honed marble tiles and honed limestone tiles look just like the surface of the tile in the first place so no work required at all if you can get a factory cut edge exposed!
Now travertine tiles are a different story as travertine tiles edges are "pitted" due to the very nature of travertine tiles honeycomb structure. You can either fill the pitting with grout then finish off with the wet and dry paper as above or if you really want to go to town fill the holes with a travertine tiles repair kit like "jolly mastic" (available online) then finish off again with the wet and dry. Using grout alone will still leave slight undulations to the edge. Jolly mastic finished off with wet and dry paper will leave a perfect flat edge that is close in finish to the honed surface of the travertine tiles themselves!
I hope all this makes sense. No doubt this post will be re-visited in the future to add other tips and tricks we can think of! In the mean time if you are still unsure why not take advantage of the sales staff's installation experience if you need some expert advice on natural stone tiles installation over the phone...