{{Short description|Carbonate mineral}} {{Infobox mineral|category=Carbonate mineral|color=Blue-green, pale blue|mohs=1 to 2|system=Monoclinic|strunz=5.CB.40|formula={{chem2|Na2[Cu(CO3)2]*3H2O}}| IMAsymbol = Chna<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}</ref> |image=File:Chalconatronite-108704.jpg|caption=Chalconatronite crystals found in Bastenberg Mine, Germany|streak=Pale blue-green|gravity=2.27|references=}}
'''Chalconatronite''' is a carbonate mineral and rare secondary copper mineral that contains copper, sodium, carbon, oxygen, and hydrogen, its chemical formula is {{chem2|Na2[Cu(CO3)2]*3H2O}}.<ref name=":1">{{Cite web|url=https://www.mindat.org/min-954.html|title=Chalconatronite: Chalconatronite mineral information and data.|website=www.mindat.org|access-date=2017-06-16}}</ref> Chalconatronite is partially soluble in water, and only decomposes, although chalconatronite is soluble while cold, in dilute acids.<ref name="jstor" /> The name comes from the mineral's compounds, copper ("''chalcos''" in Greek) and natron, naturally forming sodium carbonate.<ref>{{Cite web|url=http://www.webmineral.com/data/Chalconatronite.shtml|title=Chalconatronite Mineral Data|last=Barthelmy|first=Dave|website=www.webmineral.com|access-date=2017-06-16}}</ref><ref name=":0" /> The mineral is thought to be formed by water carrying alkali carbonates (possibly from soil<ref>{{Cite journal|last1=Franke|first1=Walter|last2=Mircea|first2=Magda|date=2005-06-01|title=Plutarch's Report on the Blue Patina of Bronze Statues at Delphi: A Scientific Explanation|url=https://www.researchgate.net/publication/272309645|journal=Journal of the American Institute for Conservation|volume=44|issue=2|pages=103–116|doi=10.1179/019713605806082356|s2cid=192001746}}</ref>) reacting with bronze. Similar minerals include malachite, azurite, and other copper carbonates.<ref name="jstor">{{Cite journal|last1=Gettens|first1=R. J.|last2=Frondel|first2=C.|date=1955|title=Chalconatronite: An Alteration Product on Some Ancient Egyptian Bronzes|jstor=1504919|journal=Studies in Conservation|volume=2|issue=2|pages=64–75|doi=10.2307/1504919}}</ref> Chalconatronite has also been found and recorded in Australia, Germany, and Colorado.<ref name="pigment" /><ref>{{Cite web|url=https://www.mindat.org/loc-10556.html|title=Deremo Mine (Deremo - Snyder Mine; Deremo Shafts; Snyder Shaft), Slick Rock District, San Miguel Co., Colorado, USA|website=www.mindat.org|access-date=2018-01-24}}</ref>
== Bronze Disease == Most chalconatronite formed on bronze and silver that have been treated with either sodium sesquicarbonate or sodium cyanide<ref>{{Cite web|url=http://cameo.mfa.org/wiki/Chalconatronite|title=Chalconatronite - CAMEO|website=cameo.mfa.org|language=en|access-date=2017-06-17}}</ref> to prevent corrosion and bronze disease.<ref name=":2">{{Cite journal|title=Chalconatronite: a by-product of conservation?|journal = Studies in Conservation|volume = 27|issue = 4|last1=Horie|first1=C. V.|last2=Vint|first2=J. A.|year=1982|pages=185–186|doi=10.1179/sic.1982.27.4.185}}</ref> The mineral has also been proven to form on the surface of copper artifacts after being treated with aqueous sodium carbonate.<ref name=":1" /> This formation by using sodium sesquicarbonate is undesirable by many antique collectors, as the mineral changes the patinas of copper artifacts. When the mineral forms, it can replace copper salts within the patina, and turn the color from a rich green to a blue-green or even black.<ref name=":2" />
== Historical Occurrence == The mineral was recorded in 1955 on three bronze artifacts from ancient Egypt, which were being held in the Fogg Art Museum at Harvard. Chalconatronite was found inside of two bronze figures (one depicting a seated Sekhmet, and another one depicting a group of cats and kittens<ref name="jstor"/><ref name="art"/>) from around the late Nubian Dynasty or early Saite Period. Another chalconatronite specimen was found under a bronze censer from the late Coptic Period.<ref name="jstor"/> The chalconatronite found on the censer formed over cuprite and some atacamite crystals, which are associated minerals.<ref name="jstor" /><ref name="art" /><ref name=":0">{{Cite journal|last1=Frondel|first1=Clifford|last2=Gettens|first2=Rutherford J.|date=1955-07-08|title=Chalconatronite, a New Mineral from Egypt|journal=Science|language=en|volume=122|issue=3158|pages=75–76|doi=10.1126/science.122.3158.75|issn=0036-8075|pmid=17748802|bibcode=1955Sci...122...75F}}</ref>
Chalconatronite was also found on iron and copper Roman armor in 1982 at a site in Chester, England.<ref name="art">{{Cite book|url=https://books.google.com/books?id=yQKuSOzkLvcC&q=chalconatronite&pg=PA117|title=Copper and Bronze in Art: Corrosion, Colorants, Conservation|last=Scott|first=David A.|date=2002|publisher=Getty Publications|isbn=9780892366385|language=en}}</ref> Some of the mineral was found on a copper pin in St. Mark's Basilica, Venice<ref>{{Cite journal|last1=E.E.|first1=Staffeldt|last2=Andrea|first2=Paleni|date=1978|title=Chalconatronite, a new mineral from St, Mark's Basilica in Venice: alteration of a copper pin fitted on a lead ingot|url=http://www.bcin.ca/Interface/openbcin.cgi?submit=submit&Chinkey=10291|language=English}}{{Dead link|date=July 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and in two different Mayan paintings.<ref name="pigment">{{Cite book|url=https://books.google.com/books?id=RJnI4ld6qeoC&q=chalconatronite+pigment&pg=PA98|title=Pigment Compendium: A Dictionary and Optical Microscopy of Historical Pigments|last=Eastaugh|first=Nicholas|date=2008|publisher=Routledge|isbn=9780750689809|language=en}}</ref> Along with pseudomalachite, chalconatronite was found on an illuminated manuscript from the sixteenth century.<ref name="pigment" /> Synthetic chalconatronite could have possibly been made in ancient China as a form of pigment, named "synthetic malachite". It was made by taking copper oxide and boiling it with white alum in a "sufficient amount of water". After the result is cooled, a natron solution would be added to precipitate a synthetic form of chalconatronite, as sodium copper carbonate.<ref name="pigment" /><ref name="art" />
== See also == * Atacamite * Cuprite * Patina * Botallackite * Bronze disease
== References == {{reflist}}
Category:Carbonate minerals Category:Copper(II) minerals Category:Corrosion Category:Minerals