thin-walled hollow tubes about 1/4 inch in diameter. It forms as water runs through the center and deposits rings of calcite around the tip.

A hollow stalactite in which calcite precipitates around the outside of a drip.

Hollow, elongate, generally translucent tube of calcite representing the earliest growth of stalactites. They are equal in diameter to the water drops conducted along their length.

A soda straw is a speleothem in the form of a hollow mineral tube. They grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves.