Travertine stone is a form of limestone. It often forms near hot bubbly mineral rich springs. Gas bubbles become trapped and create a pitted surface on the stone. These pitted surfaces can be filled with an epoxy or dust resin. Filling the small holes and pits gives the travertine a more finished look. A refined beauty. The stone surface can be left in its natural state with the small holes and pits unfilled. This is a warmer aged look which will acquire a beautiful patina over time.