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 ** ...

and rare secondary copper mineral that contains

copper Copper is a chemical element with the symbol Cu (from la, cuprum) 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 pinkis ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, and

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

, its

chemical formula In chemistry, 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 symbol ...

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. Similar minerals include

malachite Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fracture ...

azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carb ...

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

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

, and

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

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 a ...

sodium cyanide Sodium cyanide is a poisonous compound with the formula Na C N. 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 exploits its hi ...

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 engi ...

and

bronze disease Bronze disease is an irreversible and nearly inexorable corrosion process that occurs when chlorides come into contact with bronze or other copper-bearing alloys. It can occur as both a dark green coating, or as a much lighter whitish fuzzy or ...

. The mineral has also been proven to form on the surface of copper artifacts after being treated with aqueous sodium carbonate. 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, 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 ...

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

Sekhmet In Egyptian mythology, Sekhmet ( or Sachmis (), also spelled Sakhmet, Sekhet, Sakhet among other spellings, cop, Ⲥⲁⲭⲙⲓ, Sakhmi), is a warrior goddess as well as goddess of healing. She is depicted as a lioness. Sekhmet is a solar de ...

, and another one depicting a group of cats and kittens) from around the late Nubian Dynasty or early

Saite Period The Twenty-sixth Dynasty of Egypt (notated Dynasty XXVI, alternatively 26th Dynasty or Dynasty 26) dynasty was the last native dynasty to rule Egypt before the Persian conquest in 525 BC (although others followed). The dynasty's reign (664–525 ...

. Another chalconatronite specimen was found under a bronze censer from the late

Coptic Period The "Coptic Periodization, period" is an informal designation for Late Egypt (Roman province), Roman Egypt (3rd−4th centuries) and Byzantine Egypt (4th−7th centuries). This era was defined by the religious shifts in Culture of Egypt, Egyptian c ...

. 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 1801 by D. de Fallizen. The Atacama Desert is also the namesake of the mineral. ...

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

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

and copper Roman armor in 1982 at a site in

Chester, England Chester is a cathedral city and the county town of Cheshire, England. It is located on the River Dee, close to the English–Welsh border. With a population of 79,645 in 2011,"2011 Census results: People and Population Profile: Chester Loca ...

. Some of the mineral was found on a copper pin in St. Mark's Basilica,

Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The isla ...

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 Pseudomalachite is a phosphate of copper with hydroxyl, named from the Greek for “false” and “malachite”, because of its similarity in appearance to the carbonate mineral malachite, Cu2(CO3)(OH)2. Both are green coloured secondary minerals ...

, chalconatronite was found on an illuminated manuscript from the sixteenth century. Synthetic chalconatronite could have possibly been made in ancient China as a form of

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

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

copper oxide Copper oxide is a compound from the two elements copper and oxygen. Copper oxide may refer to: * Copper(I) oxide (cuprous oxide, Cu2O) * Copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black so ...

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 process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

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