Cacholong; be mistaken
Cacholong also known as Kalmuck Agate is a form of commonOpal although it is often mistaken for Agate or Chalcedony. A milky white colour with a Moh hardness of about 6, it is used for carving, cameos etc. Found in Austria, Czech Republic, Mongolia and Uzbekistan; its name possibly comes from a river in Uzbekistan.