Editing Flowstone (section)

===Concrete derived flowstone===
Flowstone derived from concrete, lime or mortar, can form on manmade structures, much more rapidly than in the natural cave environment due to the different chemistry involved.<ref name=Hill&Forti1997>Hill, C A, and Forti, P, (1997). Cave Minerals of the World,  (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] pp. 217 and 225</ref>
On concrete structures, these secondary deposits are the result of [[concrete degradation]],<ref>Macleod, G, Hall, A J and Fallick, A E, (1990). "An applied mineralogical investigation of concrete degradation in a major concrete road bridge". Mineralogical Magazine, Vol.54, 637–644</ref><ref name=SmithGK2016>Smith G.K., (2016). "Calcite straw stalactites growing from concrete structures", Cave and Karst Science, Vol.43, No.1, P.4-10, (April 2016), British Cave Research Association, ISSN 1356-191X</ref> when calcium ions have been leached from the concrete in solution and redeposited on the structure's surface to form flowstone, stalactites and stalagmites.<ref name=Hill&Forti1997 /> [[Carbon dioxide]] (CO<sub>2</sub>) is absorbed into the hyperalkaline leachate solution as it emerges from the concrete. This facilitates the chemical reactions which deposits [[calcium carbonate]] (CaCO<sub>3</sub>) on vertical or sloping surfaces, in the form of flowstone.<ref name=Hill&Forti1997 /><ref name=SmithGK2016 />

Concrete derived secondary deposits are classified as "[[calthemite]]s".<ref name=SmithGK2016 /> These calcium carbonate deposits mimic the forms and shapes of [[speleothem]]s, created in caves. e.g. [[stalagmite]]s, [[stalactite]]s, flowstone etc. It is most likely that calthemite flowstone is precipitated from leachate solution as [[calcite]], "in preference to the other, less stable [[polymorphism (materials science)|polymorphs]], [[aragonite]] and [[vaterite]]."<ref name=SmithGK2016 />

Other trace elements such as iron from rusting reinforcing or copper oxide from pipework may be transported by the leachate and deposited at the same time as the CaCO<sub>3</sub>.<ref name=SmithGK2016 /> This may cause the calthemites to take on colours of the leached oxides.<ref>White W.B., (1997), “Color of Speleothems”, Cave Minerals of the World, (2nd Edition) Hill C. and Forti P. [Huntsville, Alabama: National Speleological Society Inc.] 239-244</ref><ref name=SmithGK2016 />