Travertine is limestone that has been formed over a long period of time. It is porous with many visible holes. It is available in colours ranging from ivory to golden brown. The holes and cavities may be filled with matching Portland cement, coloured epoxy or polyester resins.
Travertine is a sedimentary calciferous stone formed in hot springs. Typically, hot water passes through limestone beds and takes the calcium from the limestone into suspension. It then takes that solution to the surface where the water evaporates and leaves the calcium in layer.
The stone can be cut on either a vein cut which is against the bedding and reveals the bedding planes, or a fleuri cut which is along the bedding plane and reveals a flowery, often circular, pattern. Travertine comes in several shades of creme/beige, brown, pink and gold.
These samples are just a few of the many types available. All natural stone varies in colour, pictures are examples only.