A
soda straw (or simply
straw) is a
speleothem in the form of a hollow
mineral cylindrical tube. They are also known as
tubular stalactites. Soda straws grow in places where water leaches slowly through cracks in rock, such as on the roofs of
caves. A soda straw can turn into a
stalactite if the hole at the bottom is blocked, or if the water begins flowing on the outside surface of the hollow tube.