Travertine is a natural stone such as basalt, granite, marble, limestone, slate, and sandstone. The key difference between travertine and other natural stones lies in the formation of the rock, the hardness of the stone and the appearance. Travertine is a form of limestone deposited by mineral springs, especially hot springs. It is formed by precipitation of carbonate minerals from solution in ground and surface waters, often at the mouth of a geothermally heated hot springs or in a limestone cave. HDG Building Materials sources travertine from quarries in China. Travertine rocks are dug up in quarries and broken down into large travertine blocks which are then transported to factories. In these factories. the large blocks are cut into slabs and subsequently into tiles, pavers, mosaics etc. Ultimately, specific surface finishes are applied to meet the needs of HDG customer projects.