What are they?
Limestone is a rock made up largely of calcium carbonate and is readily dissolved by water.
Water seeping through the rock picks up the calcium carbonate and the evaporation of the laden drops of water leaves a deposit that, over a great period of time, creates the beautiful stalagmites and stalactites.
Marble is also made up of calcium carbonate but formed under great pressure.
Its wonderful colours are formed from various foreign materials that mix with it before it crystalises.
Which is which?
It is easy to remember which is which with the following: When the mites run up the tights come down.