In a since, speleotherms are created the opposite way the cave around it is formed. Carbon dioxide slowly diffuses out of underground water releasing the calcite out of solution, and deposits in the ceiling, walls, and floors. Speleothems can only form in well ventilated areas where carbon dioxide is allowed to escape, thus they are not common very deep in caves. Soda straw stalactites are actually hollow, where the calcite runs through the tube and dries when it reaches the end. If the two can connect over time, they form a column .
Some columns can be fifty feet tall and thirty feet wide.
Flowstone like curtains is formed when the calcite flows in a sheet instead of dripping at one point. Curtains are often so thin that light can be seen through them.