Chalconatronite is a

carbonate mineral Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspéite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otavite CdCO3 **Rhodochrosite MnCO3 **Sider ...

and rare secondary copper mineral that contains

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

, and

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

, its

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

is Na₂Cu(CO₃)₂•3(H₂O). Chalconatronite is partially

soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

in water, and only decomposes, although chalconatronite is soluble while cold, in dilute acids. The name comes from the mineral's compounds, copper ("''chalcos''" in Greek) and

natron Natron is a naturally occurring mixture of sodium carbonate decahydrate ( Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and sodium sulfate. ...

, naturally forming sodium carbonate. The mineral is thought to be formed by water carrying alkali carbonates (possibly from soil) reacting with

bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals (such as phosphorus) or metalloid ...

. Similar minerals include

malachite Malachite () is a copper Carbonate mineral, carbonate hydroxide mineral, with the chemical formula, formula Basic copper carbonate, Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often for ...

azurite Azurite or '' Azure spar'Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)'' is a soft, deep-blue copp ...

, and other copper carbonates. Chalconatronite has also been found and recorded in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, and

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

Bronze Disease

Most chalconatronite formed on bronze and silver that have been treated with either

sodium sesquicarbonate Sodium sesquicarbonate (systematic name: trisodium hydrogendicarbonate) Na3H(CO3)2 is a double salt of sodium bicarbonate and sodium carbonate (NaHCO3 · Na2CO3), and has a needle-like crystal structure. However, the term is also applied to an ...

sodium cyanide Sodium cyanide is a compound with the formula Na C N and the structure . It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also expl ...

to prevent

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

and bronze disease. The mineral has also been proven to form on the surface of copper artifacts after being treated with aqueous

sodium carbonate Sodium carbonate (also known as washing soda, soda ash, sal soda, and soda crystals) is the inorganic compound with the formula and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water ...

. 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.

Historical Occurrence

The mineral was recorded in 1955 on three bronze artifacts from

ancient Egypt Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...

, which were being held in the

Fogg Art Museum The Harvard Art Museums are part of Harvard University and comprise three museums: the Fogg Museum (established in 1895), the Busch-Reisinger Museum (established in 1903), and the Arthur M. Sackler Museum (established in 1985), and four research ...

Harvard Harvard University is a private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher lear ...

. Chalconatronite was found inside of two bronze figures (one depicting a seated

Sekhmet In Egyptian mythology, Sekhmet ( or Sachmis , from ; ) is a warrior goddess as well as goddess of medicine. Sekhmet is also a solar deity, sometimes given the epithet "the Eye of Ra, eye of Ra". She is often associated with the goddesses Hatho ...

, and another one depicting a group of cats and kittens) from around the late Nubian Dynasty or early Saite Period. Another chalconatronite specimen was found under a bronze censer from the late

Coptic Period The "Coptic period" is an informal designation for Late Roman Egypt (3rd−4th centuries) and Byzantine Egypt (4th−7th centuries). This era was defined by the religious shifts in Egyptian culture to Coptic Christianity from ancient Egyptian re ...

. The chalconatronite found on the censer formed over

cuprite Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper. Its dark crystals with red internal reflections are in the isometric system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, ...

and some

atacamite Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described for deposits in the Atacama Desert of Chile in 1802 by Dmitri de Gallitzin. The Atacama Desert is also the namesake of the min ...

crystals, which are associated minerals. Chalconatronite was also found on

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and copper

Roman armor Ancient Times, Roman. - 017 - Costumes of All Nations (1882). The legions of the Roman Republic and Empire had a fairly standardised dress and armour, particularly from approximately the early to mid 1st century onward, when Lorica Segmentata (se ...

in 1982 at a site in

Chester, England Chester is a cathedral city in Cheshire, England, on the River Dee, close to the England–Wales border. With a built-up area population of 92,760 in 2021, it is the most populous settlement in the borough of Cheshire West and Chester. It is ...

. Some of the mineral was found on a copper pin in

St. Mark's Basilica The Patriarchal Cathedral Basilica of Saint Mark (), commonly known as St Mark's Basilica (; ), is the cathedral church of the Patriarchate of Venice; it became the episcopal seat of the Patriarch of Venice in 1807, replacing the earlier cathed ...

Venice Venice ( ; ; , formerly ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 islands that are separated by expanses of open water and by canals; portions of the city are li ...

and in two different

Mayan Mayan most commonly refers to: * Maya peoples, various indigenous peoples of Mesoamerica and northern Central America * Maya civilization, pre-Columbian culture of Mesoamerica and northern Central America * Mayan languages, language family spoken ...

paintings. Along with pseudomalachite, chalconatronite was found on an

illuminated manuscript An illuminated manuscript is a formally prepared manuscript, document where the text is decorated with flourishes such as marginalia, borders and Miniature (illuminated manuscript), miniature illustrations. Often used in the Roman Catholic Churc ...

from the sixteenth century. Synthetic chalconatronite could have possibly been made in

ancient China The history of China spans several millennia across a wide geographical area. Each region now considered part of the Chinese world has experienced periods of unity, fracture, prosperity, and strife. Chinese civilization first emerged in the Y ...

as a form of

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

, named "synthetic malachite". It was made by taking

copper oxide Copper oxide is any of several binary compounds composed of the elements copper and oxygen. Two oxides are well known, Cu2O and CuO, corresponding to the minerals cuprite and tenorite, respectively. Paramelaconite () is less well characterized. ...

and boiling it with white alum in a "sufficient amount of water". After the result is cooled, a

solution would be added to

precipitate In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemic ...

a synthetic form of chalconatronite, as sodium copper carbonate.

References

{{reflist Carbonate minerals Copper(II) minerals Corrosion Minerals

Bronze Disease

Historical Occurrence

See also

References