AskDefine | Define aragonite

Dictionary Definition

aragonite n : a mineral form of crystalline calcium carbonate; dimorphic with calcite

User Contributed Dictionary

English

Etymology

After the province Aragon in Spain, named by Abraham Gottlob Werner in 1790.

Translations

saline evaporate

References

Extensive Definition

Aragonite is a carbonate mineral, one of the two common, naturally occurring polymorphs of calcium carbonate, CaCO3. The other polymorph is the mineral calcite. Aragonite's crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals. Repeated twinning results in pseudo-hexagonal forms. Aragonite may be columnar or fibrous, occasionally in branching stalactitic forms called flos-ferri ("flowers of iron") from their association with the ores at the Carthinian iron mines. The type location for aragonite is Molina de Aragón (Guadalajara, Spain), 25 km outside Aragon. An aragonite cave, the Ochtinská Aragonite Cave, is situated in Slovakia. In the USA, stalactitic aragonite is known from Carlsbad Caverns. Massive deposits of oolitic aragonite are found on the seabed in the Bahamas.
Aragonite forms naturally in almost all mollusk shells, and as the calcareous endoskeleton of warm- and cold-water corals (Scleractinia). Because the mineral deposition in mollusk shells is strongly biologically controlled, some crystal forms are distinctively different from those of inorganic aragonite. In some mollusks, the entire shell is aragonite; in others, aragonite forms only discrete parts of a bimineralic shell (aragonite plus calcite). Aragonite also forms in the ocean and in caves as inorganic precipitates called marine cements and speleothems, respectively. The nacreous layer of the aragonite fossil shells of some extinct ammonites forms an iridescent material called ammolite. Ammolite is primarily aragonite with impurities that make it iridescent and valuable as a gemstone.
Aragonite is thermodynamically unstable at standard temperature and pressure, and tends to alter to calcite on scales of 107 to 108 years. The young age of the California blueschists has been famously demonstrated by the finding therein of aragonite not yet reverted to calcite. The mineral vaterite, also known as μ-CaCO3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earth's surface, and decomposes even more readily than aragonite.

See also

aragonite in Bosnian: Aragonit
aragonite in Bulgarian: Арагонит
aragonite in Catalan: Aragonita
aragonite in German: Aragonit
aragonite in Estonian: Aragoniit
aragonite in Spanish: Aragonito
aragonite in Esperanto: Aragonito
aragonite in French: Aragonite
aragonite in Galician: Aragonita
aragonite in Italian: Aragonite
aragonite in Hebrew: ארגוניט
aragonite in Lithuanian: Aragonitas
aragonite in Hungarian: Aragonit
aragonite in Dutch: Aragoniet
aragonite in Japanese: アラレ石
aragonite in Low German: Aragonit
aragonite in Polish: Aragonit
aragonite in Portuguese: Aragonita
aragonite in Romanian: Aragonit
aragonite in Russian: Арагонит
aragonite in Slovak: Aragonit
aragonite in Serbian: Арагонит
aragonite in Finnish: Aragoniitti
aragonite in Tamil: அரகோனைட்
aragonite in Vietnamese: Aragonit
aragonite in Ukrainian: Арагоніт
aragonite in Chinese: 霰石
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