Xir'tan was a continent on Vulcan.
It was the smallest of the three continents on the Vulcan home world and was noted as being somewhat larger than its counterpart on Earth, namely the land called Australia. The region was the most tectonically unstable landmass on the planet with frequent earthquakes along with over forty active volcanoes among its jagged hills. The island of Xir'tan was too unstable for permanent homes for more than a handful of Vulcans but the constant seismic activity also made it an important source for metals as well as minerals.
Vulcan legend often stated that a wanderer could simply pluck Kevas stones the size of fists from the grounds of Xir'tan. By the modern era, the Vulcan Mining Institute along with private companies often assembled X-teams to locate as wel as work at these veins when they appeared. (Last Unicorn RPG module: The Way of Kolinahr: The Vulcans)