Travertine is a form of limestone that is characterized by pitted holes and troughs in its surface, as well as its relative softness compared to other natural stones. Although the hardness varies, it will scratch. Travertine is not as soft as soapstone but it can’t compete with the hardness of granite. It is sometimes referred to as travertine limestone or travertine marble ~ although travertine is properly classified as a type of limestone, not marble.
Travertine is the terrestrial (land) formed version of limestone as opposed to the marine based formations of many other limestone varieties. Like marble, it is a calcium carbonate base and is vulnerable to alteration by exposure to mild acids. A wide variety of stones are included in this group and absorption varies from slight (less than 1%) to high (more than 10%). The combination of acid sensitivity and absorption limit the number of varieties of limestone that are suitable for countertop applications. The user of travertine countertops should be well educated in its properties to accurately anticipate its behavior in service.