speleothem: A secondary mineral deposited in a cave by the action of water.
Also known as cave formation.
From: Sybil P. Parker ed. (1997):
McGraw-Hill Dictionary of Geology and Mineralogy, 380 pages, McGraw-Hill; ISBN: 0070524327
amazon.com
The most common speleothems consist of
calcite (CaCO3),
aragonite (CaCO3) or
gypsum (CaSO4).
Some common types are: