Azurite or ''

Azure spar Azure spar, sometimes azur-spar, is a trivial and commercial, partly obsolete name for several of the most famous bright blue or blue-colored minerals, which also have similar names, most notably for lazurite and azurite,''Krivovichev V. G.'' Mi ...

''''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

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 ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

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 Lyon (Franco-Provençal: ''Liyon'') is a city in France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of the French Alps, southeast of Paris, north of Marseille, southwest of Geneva, Switzerland, north ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. The mineral, a basic

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

with the chemical formula Cu₃(CO₃)₂(OH)₂, has been known since ancient times, and was mentioned in

Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

's ''

Natural History Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

'' under the Greek name (κυανός: "deep blue," root of English

cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...

) and the Latin name ''

caeruleum Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...

''. Copper (Cu²⁺) gives it its blue color.

Mineralogy

Azurite has the formula Cu₃(CO₃)₂(OH)₂, with the copper(II)

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s linked to two different anions,

and

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...

. It is one of two relatively common basic copper(II)

carbonate minerals 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 ...

, the other being bright green

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 ...

Aurichalcite Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is . The zinc to copper ratio is about 5:4. Copper (Cu2+) gives aurichalcite its green-blue colors. Occurrence Aurichalci ...

is a rare basic carbonate of copper and

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

. Simple copper carbonate (CuCO₃) is not known to exist in nature, due to the high affinity of the ion for the

anion . Azurite crystallizes in the

monoclinic system In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic sys ...

. Large crystals are dark blue, often prismatic. Azurite specimens can be massive to nodular or can occur as

drusy In geology and mineralogy, druse is a crystal habit represented by the coating of fine crystals on a rock fracture surface, or vein or within a vug or geode. See also * Miarolitic cavity Miarolitic cavities (or miarolitic texture) are typicall ...

crystals lining a cavity. Azurite has a

Mohs hardness The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

of 3.5 to 4. The

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of azurite is 3.7 to 3.9. Characteristic of a carbonate, specimens effervesce upon treatment with hydrochloric acid. The combination of deep blue color and effervescence when moistened with hydrochloric acid are identifying characteristics of the mineral.

Color

The optical properties (color, intensity) of minerals such as azurite and malachite are characteristic of copper(II). Many

coordination complexes A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or ...

of copper(II) exhibit similar colors. According to

crystal field theory In inorganic chemistry, crystal field theory (CFT) describes the breaking of degeneracies of electron orbital states, usually ''d'' or ''f'' orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). ...

, the color results from low energy d-d transitions associated with the d⁹ metal center.

Weathering

Azurite is unstable in open air compared to malachite, and often is

pseudomorph In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced b ...

ically replaced by

. This weathering process involves the replacement of some of the carbon dioxide (CO₂) units with water (H₂O), changing the carbonate:hydroxide ratio of azurite from 1:1 to the 1:2 ratio of malachite: : 2 Cu₃(CO₃)₂(OH)₂ + H₂O → 3 Cu₂(CO₃)(OH)₂ + CO₂ From the above equation, the conversion of azurite into malachite is attributable to the low partial pressure of carbon dioxide in air. Azurite is quite stable under ordinary storage conditions, so that specimens retain their deep blue color for long periods of time.

Occurrences

Azurite is found in the same geologic settings as its sister mineral, malachite, though it is usually less abundant. Both minerals occur widely as

supergene A supergene is a chromosomal region encompassing multiple neighboring genes that are inherited together because of close genetic linkage, i.e. much less recombination than would normally be expected. This mode of inheritance can be due to genomic ...

copper minerals, formed in the

oxidized Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

zone of copper ore deposits. Here they are associated with

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, ...

native copper Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native coppe ...

, and various

iron oxide An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron ...

minerals. Fine specimens can be found at many locations. Among the best specimens are found at

Bisbee, Arizona Bisbee is a city in and the county seat of Cochise County, Arizona, Cochise County in southeastern Arizona, United States. It is southeast of Tucson, Arizona, Tucson and north of the Mexican border. According to the 2020 United States census, ...

, and nearby locations, and have included clusters of crystals several inches long and spherical aggregates and rosettes up to in diameter. Similar rosettes are found at

Chessy, Rhône Chessy (), also known as Chessy-les-Mines (), is a Communes of France, commune in the Rhône (department), Rhône Departments of France, department in eastern France. Chessy-les-Mines is the type locality (geology), type locality of the mineral ...

, France. The best crystals, up to in length, are found at

Tsumeb Tsumeb (; ) is a city of around 35,000 inhabitants and the largest town in the Oshikoto Region, Oshikoto region in northern Namibia. Tsumeb, since its founding in 1905, has been primarily a mining town. The town is the site of a deep mine (the ...

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

. Other notable occurrences are in

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

;

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

; the Ural and

Altai Mountains The Altai Mountains (), also spelled Altay Mountains, are a mountain range in Central Asia, Central and East Asia, where Russia, China, Mongolia, and Kazakhstan converge, and where the rivers Irtysh and Ob River, Ob have their headwaters. The ...

;

Sardinia Sardinia ( ; ; ) is the Mediterranean islands#By area, second-largest island in the Mediterranean Sea, after Sicily, and one of the Regions of Italy, twenty regions of Italy. It is located west of the Italian Peninsula, north of Tunisia an ...

; Laurion, Greece;

Wallaroo, South Australia Wallaroo is a port town on the western side of Yorke Peninsula in South Australia, northwest of Adelaide. It is one of the three Copper Triangle towns famed for their historic shared copper mining industry, and known together as "Little Corn ...

; Brazil and

Broken Hill Broken Hill is a city in the Far West (New South Wales), far west region of outback New South Wales, Australia. An inland mining city, it is near the border with South Australia on the crossing of the Barrier Highway (A32) and the Silver City Hi ...

Uses

Pigments

Azurite is unstable in air, however it was used as a blue pigment in antiquity. Azurite is naturally occurring in Sinai and the Eastern Desert of Egypt. It was reported by F. C. J. Spurrell (1895) in the following examples; a shell used as a pallet in a

Fourth Dynasty The Fourth Dynasty of ancient Egypt (notated Dynasty IV) is characterized as a "golden age" of the Old Kingdom of Egypt. Dynasty IV lasted from to c. 2498 BC. It was a time of peace and prosperity as well as one during which trade with othe ...

(2613 to 2494 BCE) context in

Meidum Meidum, Maydum or Maidum (, , ) is an archaeological site in Lower Egypt. It contains a large pyramid and several mudbrick mastabas. The pyramid was Egypt's first straight-sided one, but it partially collapsed in ancient times. The area is locate ...

, a cloth over the face of a Fifth Dynasty (2494 to 2345 BCE) mummy also at

and a number of

Eighteenth Dynasty The Eighteenth Dynasty of Egypt (notated Dynasty XVIII, alternatively 18th Dynasty or Dynasty 18) is classified as the first dynasty of the New Kingdom of Egypt, the era in which ancient Egypt achieved the peak of its power. The Eighteenth Dynasty ...

(1543–1292 BCE) wall paintings. Depending on the degree of fineness to which it was ground, and its basic content of copper carbonate, it gave a wide range of blues. It has been known as ''mountain blue'', ''Armenian stone'', and ''azurro della Magna'' (''blue from Germany'' in

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...

). When mixed with oil it turns slightly green. When mixed with

egg yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

it turns green-grey. It is also known by the names '' blue bice'' and ''blue verditer'', though '' verditer'' usually refers to a pigment made by chemical process. Older examples of azurite pigment may show a more greenish tint due to weathering into malachite. Much azurite was mislabeled ''

lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...

'', a term applied to many blue pigments. As chemical analysis of paintings from the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...

improves, azurite is being recognized as a major source of the blues used by medieval painters. Lapis lazuli (the pigment ultramarine) was chiefly supplied from Afghanistan during the Middle Ages, whereas azurite was a common mineral in Europe at the time. Sizable deposits were found near Lyons, France. It was mined since the 12th century in

Saxony Saxony, officially the Free State of Saxony, is a landlocked state of Germany, bordering the states of Brandenburg, Saxony-Anhalt, Thuringia, and Bavaria, as well as the countries of Poland and the Czech Republic. Its capital is Dresden, and ...

, in the silver mines located there. Heating can be used to distinguish azurite from purified natural

ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...

blue, a more expensive but more stable blue pigment, as described by

Cennino D'Andrea Cennini Cennino d'Andrea Cennini (; – before 1427) was an Italian painter influenced by Giotto. He was a student of Agnolo Gaddi in Florence. Gaddi trained under his father, called Taddeo Gaddi, who trained with Giotto. He is remembered mainly f ...

. Ultramarine withstands heat, whereas azurite converts to black copper oxide. However, gentle heating of azurite produces a deep blue pigment used in Japanese painting techniques. Azurite pigment can be synthesized by precipitating

copper(II) hydroxide Copper(II) hydroxide is the hydroxide of copper with the chemical formula of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consist ...

from a solution of

copper(II) chloride Copper(II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula . The monoclinic crystal system, monoclinic yellowish-brown anhydrous form slowly absorbs moisture to form the orthorhombic blue-green hydrate, ...

with

lime Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...

(

calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed with water. Annually, approxim ...

) and treating the precipitate with a concentrated solution of

potassium carbonate Potassium carbonate is the inorganic compound with the formula . It is a white salt, which is soluble in water and forms a strongly alkaline solution. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used ...

and lime. This pigment is likely to contain traces of basic copper(II) chlorides. File:Azuritepigment.jpg, Ground azurite for use as a pigment File:Lady with a Squirrel.jpg, The background of ''Lady with a Squirrel'' by

Hans Holbein the Younger Hans Holbein the Younger ( , ; ; – between 7 October and 29 November 1543) was a German-Swiss painter and printmaker who worked in a Northern Renaissance style, and is considered one of the greatest portraitists of the 16th century. He ...

was painted with azurite File:Madonna and Child Enthroned with Saints.jpg, The greenish tint of the Madonna's mantle in

Raphael Raffaello Sanzio da Urbino (; March 28 or April 6, 1483April 6, 1520), now generally known in English as Raphael ( , ), was an Italian painter and architect of the High Renaissance. List of paintings by Raphael, His work is admired for its cl ...

's ''Madonna and Child Enthroned with Saints'' is due to azurite weathering to malachite

Jewelry

Azurite is used occasionally as beads and as

jewelry Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the ...

, and also as an ornamental stone. However, its softness and tendency to lose its deep blue color as it weathers leaves it with fewer uses. Heating destroys azurite easily, so all mounting of azurite specimens must be done at room temperature.

Collecting

The intense color of azurite makes it a popular collector's stone. The notion that specimens must be carefully protected from bright light, heat, and open air to retain their intensity of color over time may be an

urban legend Urban legend (sometimes modern legend, urban myth, or simply legend) is a genre of folklore concerning stories about an unusual (usually scary) or humorous event that many people believe to be true but largely are not. These legends can be e ...

. Paul E. Desautels, former curator of gems and minerals at the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

, has written that azurite is stable under ordinary storage conditions.

Prospecting

While not a major ore of copper itself, the presence of azurite is a good surface indicator of the presence of weathered

copper sulfide Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores. Prominent copper sulfide minerals ...

ores. It is usually found in association with the chemically similar malachite, producing a striking color combination of deep blue and bright green that is strongly indicative of the presence of copper ores.

History

Azurite was known in the pre-classical

ancient world Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient h ...

. It was used in

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 ...

as a pigment, obtained from mines in Sinai.

Ancient Mesopotamia The Civilization of Mesopotamia ranges from the earliest human occupation in the Paleolithic period up to Late antiquity. This history is pieced together from evidence retrieved from archaeological excavations and, after the introduction of writ ...

n writers report the use of a special

mortar and pestle A mortar and pestle is a set of two simple tools used to prepare ingredients or substances by compression (physics), crushing and shear force, grinding them into a fine Paste (rheology), paste or powder in the kitchen, laboratory, and pharmacy. ...

for grinding it. It was also used in ancient

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

, for example on the

Acropolis An acropolis was the settlement of an upper part of an ancient Greek city, especially a citadel, and frequently a hill with precipitous sides, mainly chosen for purposes of defense. The term is typically used to refer to the Acropolis of Athens ...

in Athens. It does not appear to have been used in

ancient Roman In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Em ...

wall paintings but Roman writers certainly knew about its use as a pigment. The fusing of glass and azurite was developed in ancient Mesopotamia.Emmerich Paszthory, "Electricity generation or magic? The analysis of an unusual group of finds from Mesopotamia", p. 34 in, Stuart J. Fleming, Helen R. Schenck, ''History of Technology: The Role of Metals'', University of Pennsylvania Museum of Archaeology, 1989 .

Gallery

Azurite from China.jpg, Azurite crystals from China File:Azurite from Arizona, collected by Dr John Hunter in the 18th century, Hunterian Museum, Glasgow.jpg, Azurite from Arizona, collected by Dr John Hunter in the 18th century, Hunterian Museum, Glasgow File:Mineraly.sk - azurit.jpg, Fresh, unweathered azurite crystals showing the deep blue of unaltered azurite. From

Špania Dolina Špania Dolina is a village and municipality in central Slovakia, near the city of Banská Bystrica. Although its permanent population does not exceed 200 people, it is a picturesque historic village situated 728 m above sea level and is surrounded ...

Slovakia Slovakia, officially the Slovak Republic, is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the west, and the Czech Republic to the northwest. Slovakia's m ...

File:Azurite with Malachite - National Museum of Natural History - Washington, D.C..jpg, Azurite with Malachite, Copper Queen mine,

File:Azurite-23164.jpg, Azurite from Touissit, Morocco File:Azurite-284714.jpg, Azurite,

Morenci, Arizona Morenci is a census-designated place (CDP) and company town in Greenlee County, Arizona, United States, and was founded by the Detroit Copper Mining Company of Arizona. The population was 2,000 at the 2000 census and 1,489 at the 2010 census ...

File:Azurite in siltstone, Malbunka mine NT.jpg, Azurite in

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

, Malbunka mine,

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

, Australia File:Azurite-den07-03b.jpg, Azurite from

, Namibia File:Azurite Bisbee ROM.jpg, Azurite, cross-section through merged

stalactite A stalactite (, ; , ) is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension (chemistry ...

File:Batu Azurite.jpg, Azurite from

Bandung Bandung is the capital city of the West Java province of Indonesia. Located on the island of Java, the city is the List of Indonesian cities by population, fourth-most populous city and fourth largest city in Indonesia after Jakarta, Surabay ...

, Indonesia File:Sparkly Azurite Crystal 01.jpg, Azurite crystal, from the minerals collection at the

Natural History Museum, London The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum (Lo ...

. File:Azurite spheroids.jpg, Spheroidal azurite specimens from

References

External links

*
Azurite
Colourlex {{Authority control Carbonate minerals Copper ores Gemstones Monoclinic minerals Minerals in space group 14