Rimstone

Rimstone, also called gours, is a type of speleothem (cave formation) in the form of a stone dam.

These secondary deposits consisting primarily of calcium carbonate, are called calthemites and mimics the shapes and forms of cave speleothems to create stalactites, stalagmites, flowstone and gours.

The leachate which does reach the ground usually evaporates quickly due to air movement beneath the concrete structure, hence micro-gours are more common.

[2] Calcium carbonate deposition as micro-gours occur when the solution drops to the ground under the concrete structure.

Secondary deposits, which create stalagmites, stalactites, flowstone, rimstone etc., outside the natural cave environment, are referred to as “calthemites”.