Cacholong, also known as Kalmuck agate, is a form of common opal, although it is often mistaken for agate or chalcedony, and Parker Cleaveland claimed it was a variety of chalcedony.: 249 It has a milky white colour that can also be described as bluish white or cream. With a Mohs hardness of about 6, it is used for carving, cameos, etc. The word "cacholong" has also been used as a synonym for actinolite.
Found in Austria, Czech Republic, Mongolia and Uzbekistan, its name possibly comes from the Cach River in Bukhara.: 249 It is also known to occur in Iceland; in the town of Huttenberg, Austria; in Deerfield: 249 and Pittsfield, Massachusetts, U.S.; in the Faroe Islands; in Elba, Italy; and in Spain; and in Nova Scotia, Canada.
The gemstone sculpture Sultry Midday by Vasily Konovalenko, which depicted two women having tea, incorporated a cacholong teacup.