travertine
A calcium-carbonate stone deposited from water, used as decorative natural stone and sometimes called travertine marble.
Often referred to as travertine marble, this stone is actually more closely related to limestone but its impurities can give it a marble-like appearance. Formed in water from calcium carbonate deposits, travertine forms as dissolved calcium carbonate precipitates from the water. The stone takes a polish and is used for its decorative effect, especially in building lobbies.
The stone forms through mineral deposition from water. That origin differs from the metamorphic formation of marble, despite the overlapping commercial terminology.
A polished surface or marble-like pattern does not change the material. Its common decorative use in lobbies also does not limit the facade designation to an interior application.