What is a limestone that is dripped from the ceiling of a cave forming a peak or column?

The limestone, or more accurately its calcium carbonate,has been dissolved from the rock above, in the joints through which the ground-water passes before dripping into the cave.

The mineral is then precipitated in the cave air as Calcite, to form a Stalactite on the celing, and a Stalagmite on the floor below.

A "column" is simply a stalactite and stalagmite that have met.