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 still scratch. It’s not as soft as soapstone but it can’t compete with the hardness of granite. It is sometimes known as travertine limestone or travertine marble; these are the same stone, although travertine is classified properly as a type of limestone, not marble. It is actually the terrestrial (land) formed version of limestone, as opposed to the marine based formations of many other limestone varieties. Travertine, like marble, is of a calcium carbonate base, and as such, is vulnerable to alteration by exposure to mild acids. A wide variety of stones are included in this group, and absorption varies from slight to high. The combination of acid sensitivity and absorption limit the number of varieties that are suitable for counter top applications, and the user of limestone counter tops should be well educated in its properties to accurately anticipate its behavior in service.