Stalactites are normally associated with caves, primarily limestone cave that had or have water movement. Carlsbad Caverns in New Mexico is one of the more stunning examples of stalactite and stalagmite formation in North America. The keywords involved in the formation of these fantastic spires are “limestone” and “water”, the water draws the minerals out of the limestone and as it drips from the ceiling small accretions (stalactites) form as the minerals are deposited. The floor collects other deposits which build up into stalagmites, eventually the two may actually meet form a column.
You may be wondering what this little science lesson has to do with urban and exploring, right? I’ll just take a moment to point out that concrete is made from cement, which in turn is made from (taadaa!) limestone. So happens to all these old concrete buildings after they have been abandoned to elements for 50 years?
Since the color of the stalactite is dictated by which minerals go into its composition in areas of high iron content you will even get beautiful red and orange stalactites hanging from the ceiling of an abandoned furniture store.