Origin of name: Named after the place of discovery - the province of Aragon in Spain.

Varieties of the mineral:

Aragonite coral-like or iron flower (flos-feri) with white branches resembling coral. Aragonite pisolithic in the form of spherical constrictions. pea stone, caviar stone, sprudelstein - cemented aragonite oolites. Conhit - main component(along with chitin) pearls and a mother-of-pearl layer of mollusk shells. Nicholsonite - zinc variety of aragonite, has a red-brown or purple color. Tarnovicite A lead-containing variety of aragonite.

Sample photos

Properties

Syngony: Rhombic

Composition (formula): CaCO 3 , typical impurities are Sr, Mg, Fe, Zn, Pb.

Color:

White, colorless, grey, yellowish, reddish

Dash color (powder color): White

Transparency: Transparent, Translucent

Cleavage: Imperfect

Fracture: Conchoidal

Gloss: Bold, Glassy

Hardness: 3.5-4

Specific gravity, g / cm 3: 2,9-3,0

Special properties:

If aragonite is heated in dry air, then at a temperature of 400 ° C it will begin to transform into calcite. Thermoluminescent.

Selection form

Aragonite crystals are acicular, prismatic, spear-shaped. Often, aragonite forms crystalline intergrowths, radially radiant, columnar and stellate aggregates, accumulations of oolites, and spherulites. Aragonite is typical for karst caves, occurs there in the form of crystalline crusts, forms helictites, crystallictites and corallites. Mother-of-pearl and pearls are made of thin layers of aragonite.

Main diagnostic features

Aragonite "boils" in dilute cold acids. Unlike calcite, it does not have perfect cleavage along the rhombohedron. Separate samples of aragonite luminesce in ultraviolet rays.

Origin

Low-temperature hydrothermal, sedimentary, supergene, biogenic

Deposits / manifestations

Aragonite deposits are known in Germany(Harz), Austria(Carinthia), Czech Republic(Karlovy Vary), Italy, Spain, France and many other places

Application

A pearl composed of aragonite is a first class gemstone. In addition, aragonite is a spectacular collection material.

Aragonite- is one of the natural polymorphic modifications of calcium carbonate (rhombic polymorphic modification of calcite). Trimorphene with calcite and vaterite, but less common. Chemical composition - content (in%): CaO -56; CO 2 - 44; impurities of strontium, magnesium, and iron are noted.
Prismatic crystals, from short to long prismatic, acicular-pyramidal and lamellar intergrowths-bundles of acicular crystals; spear-shaped, needle-shaped. Often forms crystalline intergrowths, columnar and parallel fibrous, sheaf-like, radially radiant and stellate aggregates, spherulites, accumulations of oolites. It is common in karst caves, where it occurs in the form of crystalline crusts, forms helictites, crystallictites and corallites (the so-called "iron flowers" - aggregates of branching white or yellowish stems found in karst caves). Forms polysynthetic twins and tees. Mother-of-pearl and pearls are made of thin layers of aragonite.

The origin is low-temperature hydrothermal (in association with serpentine, opal, chalcedony, other carbonates), sedimentary, supergene (in association with gypsum, dolomite, clay minerals), biogenic. It often forms in voids in basalts, in deposits of hot carbonic sources, is deposited from low-temperature solutions during weathering, also in amygdules and along cracks in basaltic lavas and tuffs. It is typical for hydrocarbonate thermal springs and geysers with water temperatures up to 100°C, where it forms scales (calcareous tuffs), stalactites and oolitic pea stones. Inorganic sediments of CaCO 3 composition in shallow areas of the modern ocean in arid zones consist almost entirely of aragonite, represented by radially radiant concentric-zonal oolites formed in the wave-cut zone with constant water movement. In diagenetic calcareous sediments, marbles and carbonate metamorphic rocks, aragonite is an important constituent. The valves of sea mollusk shells are partly built from aragonite, the thinnest layers of aragonite are the basis of mother-of-pearl and pearls.
Behavior in acids dissolves in HCl with effervescence.

Mineral properties

• Origin of name: At the place of discovery in the province of Aragon, Spain.
• Opening place: Gallo river, Molina de Aragon, Guadalajara, Castile-La Mancha, Spain
• Opening year: 1797
• Thermal properties: Begins to convert to calcite around 400°C when heated in dry air.
• Luminescence: thermoluminescent; pale pink, yellow, white or bluish, with greenish or white phosphorescence (LW UV); yellowish (SW UV).
• IM status: valid, first described before 1959 (before IMA)
• Typical impurities: Sr,Pb,Zn
• Strunz (8th edition): 5/B.04-10
• Hey's CIM Ref.: 11.4.2
• Dana (7th edition): 14.1.3.1
• Molecular weight: 100.09
• Cell options: a = 4.95Å, b = 7.96Å, c = 5.74Å
• Attitude: a:b:c = 0.622: 1: 0.721
• Number of formula units (Z): 4
• Unit cell volume: V 226.17 ų
• Twinning: Crystals are usually twinned cyclically along (110) with the formation of pseudo-hexagonal forms of intergrowth and germination of subindividuals. Polysynthetic twinning is also not uncommon, with the formation of lamellar multilevel packs in parallel
• Dot group: mmm (2/m 2/m 2/m) - Rhombo-dipyramidal
• Density (calculated): 2.944
• Density (measured): 2.947
• Optical axis dispersion: weak
• Refractive indices: nα = 1.529 - 1.530 nβ = 1.680 - 1.682 nγ = 1.685 - 1.686
• Maximum birefringence:δ = 0.156
• Type: biaxial (-)
• angle 2v: measured: 18° to 19°, calculated: 16° ​​to 18°
• Optical Relief: high
• Selection form: prismatic, acicular-pyramidal, spear-shaped crystals, lamellar intergrowths-bundles of acicular crystals; crystalline intergrowths, radial-radiant and stellate aggregates, spherulites, accumulations of oolites.
• Classes according to the systematics of the USSR: Carbonates
• IMA classes: Carbonates
• Chemical formula: CaCO 3
• Syngony: rhombic
• Color: white, gray, pale yellow, green, blue, purple, black.
• Dash color: white, light grey.
• Shine: glass resin
• Transparency: transparent translucent translucent
• Cleavage: average over (010)
• Break: conchoidal
• Hardness: 3,5 4
• Fragility: Yes
• Literature: Alexander (1940) American Journal of Science: 238: 366. Haberlandt (1940) Chemie der Erde, Jena: 13: 212. Kleber (1940) Neues Jahrbuch für Mineralogie, Geologie und paleontologie, Beil.-Bd., Heidelberg, Stuttgart: 75: 465. Alexander (1941) Gemmologist: 10: 93. Alexander (1941) Science: 93: 110. Yugovics (1941) Földtani Közlöny, Budapest (Magyarhone Földtani Torsulat): 71: 23. Andrew and Schaller (1942) American Mineralogist : 27: 135. Melmore (1942) Nature: 150: 382. Bray (1945) Journal of the Royal Society of new South Wales: 78: 113. Hugi (1945) Schweizerische mineralogische und petrographische Mitteilungen, Frauenfeld: 25: 114. Zavaritzky (1948) Doklady of the Academy of Sciences of the USSR, Earth Science Sections: 63: 725. Faust (1950) American Mineralogist: 35: 207. Palache, C., Berman, H., & Frondel, C. (1951) , The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphat es, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 182-193. American Mineralogist (1971): 56: 758-772. Gaines, Richard V., H. Catherine, W. Skinner, Eugene E. Foord, Brian Mason, Abraham Rosenzweig (1997), Dana's New Mineralogy: The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, 8th. edition : 442. Reviews in Mineralogy, Mineralogical Society of America: 11. Jiménez, R., Calvo, M., Martínez, M.A. and Gorgues, R. (2005. Yacimientos de aragonito del triásico español. Bocamina,(16), 28- 93

Photo of the mineral

Calcite - aragonite group

Named after an occurrence near Molina in the historical region of Aragon (Spain), where it was first discovered. English name Aragonite.

Aragonite formula

Chemical composition

Same as calcite: calcium oxide (CaO) 56.0%, carbon dioxide (CO 2 ) 44.0%; aragonite often contains impurities of strontium (up to 5.6%), magnesium, iron, and zinc.

Crystallographic characteristic

Syngony. Rhombic (pseudohexagonal).

Symmetry class. Rhombo-bipyramidal mmm. V. With. 3L23PC. Etc. gr. Pmcn(D162h). a0 = 4.94; b0 = 7.94; c0 = 5.72. Axis ratio. 0.622:1:0.720.

Crystal structure

The aragonite structure is denser than the calcite structure. As in the calcite lattice, in the aragonite lattice each CO 3 ion is surrounded by six calcium ions.

Main forms: Main forms: prism (110), pinacoids (010)f and (001). The latter is covered with strokes parallel to the a axis. The following forms are often found: a prism (011), which sharpens the crystals like a chisel, a dipyramid (111), in some cases very sharp dipyramids in combination with prisms, as a result of which the crystals take on a spear shape

Form of being in nature

The appearance of the crystals is prismatic, often pseudohexagonal, acicular. The shape of the crystal head is chiselled.

Twins are often observed in (110). Tees of a pseudo-hexagonal shape, quadruples and complex polysynthetic twins are also common. In this case, incoming angles in the form of grooves are usually formed between the faces of the prisms. Untwinned crystals are very rare.

Aggregates. Fibrous, shelly, dense, oolitic. Aggregates are often represented by columnar, radially radiant and stellate intergrowths of individuals. It is also observed in the form of crystalline crusts, sinter, spherical forms and in masses of oolitic structure (“pea” and “caviar stones”). Cave formations sometimes found in the form of intertwined and branching "stems" of snow-white color are very original. Finally, the inner mother-of-pearl parts of most mollusk shells are built from the thinnest plates of aragonite, parallel to the surface of the shell. As you know, grains of sand or other foreign bodies that get inside the shell are covered with layers of similar carbonic lime with an admixture of organic matter, resulting in the formation of pearl nodules.

Branched (iron flowers), crusts, spherulites (pea stone); the differences refer to sprudelsteins.

Physical Properties

Optical

• Color. White, gray, pale yellow, with a reddish tint, green, blue, purple, black.
• Damn. White, light grey.
• Glass luster.
• The ebb is silky, oily in the break.
• Transparency. Water-transparent, cloudy, translucent.
• Individual crystals are often clear and colorless.

In cathode rays, it glows a faint pale violet, sometimes orange.

Refractive indices

Ng = 1.686, Nm = 1.681 and Np = 1.530.

Mechanical

• Hardness. 3.5-4. Fragile.
• Density. 2.95. 2.9–3.0 (greater than that of calcite, indicating a denser packing of atoms).
• Cleavage. Imperfect on (010) and barely noticeable on (110) and (011).
• The fracture is often conchoidal.

Chemical properties

behavior in acids. Easily soluble in HCl (with active effervescence).

In acids, it decomposes with rapid release of carbon dioxide. Aragonite powder (as well as strontianite and witherite) in a solution of cobalt nitrate becomes purple upon boiling (Meigen reaction), while calcite powder almost does not change or turns bluish or greenish, and then only with long boiling.

Other properties

Unstable at normal temperature; in the presence of a solvent, it slowly transforms into calcite, which is why it is not found in older sediments. As the temperature rises to 400°C, this transition occurs rapidly. It is curious that the varieties of aragonite that have not undergone a polymorphic transformation into calcite contain larger strontium ions (up to several percent), which, according to R. J. Hayuy and N. V. Belov, obviously has a stabilizing effect on the stability of this modification. . More soluble in water than calcite.

Diagnostic features

Similar minerals. Calcite, strontianite, celestite, barite, natrolite, topaz.

In color and behavior in HCl, it is very similar to calcite, but differs from it in the absence of cleavage along the rhombohedron and in the appearance of crystals with characteristic, sometimes thin grooves on the faces of the prism and increased hardness. Zeolites similar to it (hydrous silicates of Na, Ca, etc.) do not emit into hydrochloric acid CO2. Witherite and strontianite have a higher specific gravity and melt in front of the blowpipe.

Associated minerals. Siderite (iron spar), limonite, copper pyrite, gypsum, sulfur

Origin and location

It is formed in cracks and in amygdules of basalts, trachyphonolites; in hydrothermal deposits of siderite; sometimes inclusions in gypsum-bearing and clay deposits; in deposits of thermal springs (limescale sprudelstein, pea stone); in the thermal springs of Karlovy Vary; widespread throughout.

Aragonite is much rarer in nature than calcite.. As one of the lowest temperature minerals, it is quite often formed during damped hydrothermal processes. Such, for example, are his finds in fissures among serpentinized ultramafic rocks, without any connection with surface processes. The same formations include finds of small needlelike crystals of aragonite in voids, among basalts unaffected by decomposition, occasionally in marbles, volcano lavas, deposits from hot, supersaturated Ca[CO 3 ] mineral springs in the form of calcareous tuff or oolites (“pea stone” Karlovy Vary springs in the Czech Republic), etc.
However, in the bulk aragonite It is formed during various exogenous processes, often with the participation of dissolved magnesian salts. In the form of radially radiant formations and sinter forms, often large sizes, it is widely distributed in the weathering crust of ultramafic magnesian igneous rocks in association with dolomite, gypsum, argillaceous matter, and other minerals of exogenous origin. It is observed in voids among brown iron ore in the form of overgrown small crystals and in the form of "iron flowers", for example, in the Bakalskoye deposit (South Ural), in gypsum-bearing strata, in deposits of native sulfur, etc.

Practical use

ornamental stone

Physical research methods

Calcium carbonate is an inorganic chemical compound, which is represented in nature by such minerals as calcite, aragonite, vaterite. Aragonite is second in popularity after calcite.

It forms at low temperatures close to the earth's surface, such as in stalactite caves. It has the same chemical composition as calcite, but differs from it in structure. Aragonite is harder than calcite and is easily recognizable by its hexagonal prismatic tees.

History of the mineral

Legend has it that the tears of a girl who was separated from her lover and not allowed to marry her lover turned into aragonite. Aragonite tears were shed in the Spanish ancient city of Molina de Aragon.

The first mention of this mineral is found in the book of Father José Torrubia "Introduction to the natural history of Spain" (Madrid, 1754). In mineralogy, aragonite was immortalized by the Saxon geologist Abraham Gottlob Werner (1749–1818), who erroneously assumed that this city was located in the ancient kingdom of Aragon, and not in Castile. No one began to dissuade him from an erroneous opinion, and the mineral remained with this name.

Types and colors of aragonite

Aragonite and its magical properties

Medicinal properties

The mineral can be called a healing crystal. If you use it as a healing agent, then you need to protect it from negative energy. Aragonite is placed either in the room of a sick person, or carried with them. It helps relieve fever, inflammation, reduce fever. Acting as a mediator, helps relieve stress, has a good effect on nervous system. Helps to fight such an ailment as chronic fatigue. Relieves insomnia, irritation and anger. Helps with hair loss. Warms the limbs, stops muscle spasms and twitching. They treat skin diseases - from allergic reactions to lichen and psoriasis.

Despite the same chemical composition, aragonite and calcite have different crystal lattices, and therefore the properties of minerals differ. Aragonite forms prismatic, columnar, tabular, acicular and spear-shaped crystals. The aggregates are radially radiant, columnar, fibrous, fine-grained. Twinned crystals, multiple complex twins, polysynthetic twins are common.

Aragonite is an unstable phase of calcium carbonate, and over a period of time of the order of 10 - 100 million years it changes to calcite. The transformation of aragonite into calcite is accompanied by an increase in volume. When heated above 400 ° C, a rapid transition of aragonite into calcite occurs, and on fire it crumbles into fine calcite powder.

Links

• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
• Aragonite in the GeoWiki encyclopedia (Russian)
• Aragonite on Crystals.NET (rus.)
• Aragonite in the webmineral.com database (eng.)

Wikimedia Foundation. 2010 .

Synonyms:

See what "Aragonite" is in other dictionaries:

The mineral is lime carbonate, which forms lime deposits at hot springs. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. ARAGONITE mineral, carbonic lime, forms carbonic precipitation in hot ... ... Dictionary of foreign words of the Russian language

- [in Aragon, Spain] ml, CaCO3. Ca is partially replaced by Sr, Pb, and Zn, occasionally by Ba and Mg; lead content A. tarnowitzite, zinc soder. A. nicolsonite. Rhombus. Kly prism., needle-shaped, lamellar, thick tabular. Dv. according to (110), sometimes ... ... Geological Encyclopedia

Mineral of the carbonate class, CaARAGUA (Aragua) state in the north of Venezuela. The area is 7 thousand km². Population 1.2 million (1990). Adm. c. Maracay … Big encyclopedic Dictionary

- (CaCO3), carbonate mineral, calcium carbonate. It is formed in special conditions, in caves and hot springs. The shells of modern mollusks are composed of aragonite. It easily turns into calcite (another CaCO3 mineral). It is found as... Scientific and technical encyclopedic dictionary

Exist., number of synonyms: 2 mineral (5627) tarnovicite (2) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary

aragonite- Mineral (calcium carbonate), forms the mineral part of mother-of-pearl, pearls and corals, as well as marble onyx of limestone caves; ornamental stone. [English Russian Gemological Dictionary. Krasnoyarsk, KrasBerry. 2007.] Topics gemology and ... ... Technical Translator's Handbook

A; m. A mineral of the carbonate class (one of its varieties is the main component of pearls and the mother-of-pearl layer of mollusk shells). * * * aragonite is a mineral of the carbonate class, Ca. Colorless, white, gray, purple to black. Hardness... ... encyclopedic Dictionary

aragonite- aragonitas statusas T sritis chemija apibrėžtis Mineralas. formulė CaCO₃ atitikmenys: engl. aragoniterus. aragonite ... Chemijos terminų aiskinamasis žodynas

- (from the Aragon region in Spain) a mineral of Ca composition, crystallizing, unlike Calcite, in a rhombic system. On the surface of the Earth, A. is unstable and gradually passes into a more stable modification of trigonal calcite. ... ... Great Soviet Encyclopedia

Rhombic system mineral (mostly a combination of prism, brachypinacoid, brachydoma, also pyramid), colorless or slightly greenish, reddish and purple. Often forms simple or repeated twins along the plane ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron