Editing Mineral spring (section)

==Deposits==
[[File:Badab Surt Najafi2.jpg|thumb|180px|right|Stepped [[travertine]] terrace formations at [[Badab-e Surt]], [[Iran]]]]
Types of [[sedimentary rock]] – usually [[limestone]] ([[calcium carbonate]]) – are sometimes formed by the [[evaporation]], or rapid [[Precipitation (meteorology)|precipitation]], of minerals from spring water as it emerges, especially at the mouths of hot mineral springs. In cold mineral springs, the rapid precipitation of minerals results from the reduction of acidity when the {{CO2}} gas bubbles out. (These mineral deposits can also be found in dried lakebeds.) Spectacular formations, including terraces, [[stalactite]]s, [[stalagmite]]s and 'frozen waterfalls' can result (see, for example, [[Mammoth Hot Springs#Mammoth Hot Springs|Mammoth Hot Springs]]).

One light-colored porous [[calcite]] of this type is known as [[travertine]] and has been used extensively in [[Italy]] and elsewhere as building material. Travertine can have a white, tan, or cream-colored appearance and often has a fibrous or concentric 'grain'.

Another type of spring water deposit, containing [[siliceous]] as well as [[calcareous]] minerals, is known as [[tufa]]. Tufa is similar to travertine but is even softer and more porous.

[[Chalybeate|Chaybeate springs]] may deposit iron compounds such as [[limonite]]. Some such deposits were large enough to be [[Chalybeate Spring, Mittagong#Significance|mined as iron ore]].