Travertine Finish
In honed travertine tile, holes in the stone from which this tile is cut are filled with epoxy resin. Then the stone is given a flat finish by honing it. This process leaves the honed travertine tile with edges that are even. By contrast, these holes are left unfilled in tumbled travertine tile. Tumbled tile surfaces remain unpolished. The holes are left intact, giving the tumbled tile a more natural and rustic appearance.
Strength and Durability
Limestone, from which travertine tile is formed, is a naturally soft stone. With pockets and holes that are created from gas bubbles when the limestone is still in a molten state, this stone is left in a more weakened and vulnerable condition. When these holes are filled with epoxy resin, as done by the factory, the tile is strengthened. Tumbled travertine, with holes left unfilled, remains more vulnerable to breakage. This vulnerability in tumbled travertine can be reduced by filling the holes and cavities with grout during installation. In addition to strengthening the tile, this filling with grout also prevents the build up of debris in the stone when it is used as a decorative tile.
Source: www.DoItYourself.com