Essex Rock & Mineral Society, member's article
Hang on tight
by
Stuart Adams
Whilst in SW Spain on holiday this year I had the opportunity to take a day trip to our 300 year old colony, Gibraltar. On part of the guided tour I visited the St Michael's caves. Inside there was a spectacular feast of stalactites (they hang on tight) and stalagmites, still growing as the calcium bicarbonate rich waters slowly evaporate off their surfaces. In 1972 one of the stalactites had become so heavy that it became unstable and had fallen from the roof. Fortunately someone had had the initiative to polish a cross section revealing the growth rings. I don't know of a method to provide an age of stalactites but it will depend on temperature water flow and evaporation rates all of which will be related to the local environment. But whatever it will be slow. This is in contrast to the petrifying wells in Derbyshire where items left in the flowing waters at Matlock Bath for a few years are totally calcified.
