Editing Sodium carbonate (section)

==Occurrence as natural mineral==

[[File:Na2CO3.H2O-bas.png|160px|thumbnail|left|Structure of monohydrate at 346&nbsp;K]]
Sodium carbonate is soluble in water, and can occur naturally in arid regions, especially in mineral deposits (''evaporites'') formed when seasonal lakes evaporate. Deposits of the mineral [[natron]] have been mined from dry lake bottoms in Egypt since ancient times, when natron was used in the preparation of [[mummy|mummies]] and in the early manufacture of glass.

The anhydrous mineral form of sodium carbonate is quite rare and called natrite. Sodium carbonate also erupts from [[Ol Doinyo Lengai]], Tanzania's unique volcano, and it is presumed to have erupted from other volcanoes in the past, but due to these minerals' instability at the Earth's surface, are likely to be eroded. All three mineralogical forms of sodium carbonate, as well as [[trona]], trisodium hydrogendi carbonate dihydrate, are also known from ultra-alkaline [[pegmatite|pegmatitic rocks]], that occur for example in the [[Kola Peninsula]] in Russia.

Extra terrestrially, known sodium carbonate is rare. Deposits have been identified as the source of [[bright spots on Ceres]], interior material that has been brought to the surface.<ref>{{cite journal |title=Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres |journal=Nature |date= 29 June 2016 |last=De Sanctis |first=M. C. |display-authors=etal |volume=536 |issue= 7614|doi=10.1038/nature18290 |pages=54–57 |pmid=27362221|bibcode=2016Natur.536...54D |s2cid=4465999 }}</ref> While there are [[carbonates on Mars]], and these are expected to include sodium carbonate,<ref name="Kargel2004">{{cite book|author=Jeffrey S. Kargel|title=Mars - A Warmer, Wetter Planet|url=https://books.google.com/books?id=0QY0U6qJKFUC&pg=PA399|date=23 July 2004|publisher=Springer Science & Business Media|isbn=978-1-85233-568-7|pages=399–}}</ref> deposits have yet to be confirmed, this absence is explained by some as being due to a global dominance of low [[pH]] in previously aqueous [[Martian soil]].<ref>Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM</ref>