Dripstone (Stalactites and Stalagmites)
When water seeps into the cave and drips from the ceiling, a stalactite is the result. The first stage is a hollow soda straw stalactite. The water drop travels down the central canal of the soda straw and hangs on the end, depositing more calcite before dropping to the floor. When the hollow tube eventually plugs up, more water runs on the outside of the stalactite, making it thicker and forming a stalactite. Yet there is still some water moving internally through stalactites (hence the helictites that form on some and the recrystallization of the internal portions). If the drop of water that falls still contains calcite when it hits the ground, this may deposit as well to form a stalagmite. They tend to be squatter than stalactites. The longer the water drop hangs from the ceiling, the less likely it is to still contain calcite when it lands on the floor. Not all stalactites have stalagmites beneath them. Columns result when a stalactite and stalagmite join.