The Travertine

Travertine is a sedimentary rock. It is a natural chemical precipitate of carbonate minerals from solution in the gorundwater.
Water passes through and dissolves limestone, picking up calcium carbonate. Upon a change in temperature, the water releases its carbon dioxide as a gas and the remaining calcium carbonate recrystallizes. Biotic material such as algae then becomes encrusted with the calcium carbonate, creating the hard rock.

Travertine of Tivoli

The stone, with a light-colored (mostly white) or, occasionally, with a variety of colors from grey to coral-red, is characterised by pitted holes and troughs on its surface that are sometimes filled and polished depending on the requirements of the finished stone.
Thanks to this porosity the stone has several qualities: a low thermal conductivity, a good sound insulation and easy cutting.

The ancient name for the stone was lapis tiburtinus (from the Latin, reflecting the importance of this rock to Imperial Rome), meaning tibur stone (Tivoli was known as Tibur in ancient Roman times), which has been corrupted to travertine.
The better quality of travertine came from the quarries of Tivoli where there are several extensive deposits.