Aragonite

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Aragonite

Aragonite is a carbonate mineral, one of the two common, naturally occurring polymorphs

Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements....
of calcium carbonate

Calcium carbonate

Calcium carbonate is a chemical compound with the chemical formula CalciumCarbonOxygen3. It is a common substance found as Rock in all parts of the world, and is the main component of seashells, snails, and eggshells....
, Ca

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....
C

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
O

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
₃. The other polymorph is the mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
calcite

Calcite

Calcite is a Carbonate minerals and the most stable Polymorphism of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite....
. Aragonite's crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic system with acicular crystals. Repeated twinning

Crystal twinning

Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations....
results in pseudo-hexagonal forms. Aragonite may be columnar or fibrous, occasionally in branching stalactitic

Stalactite

A stalactite is a type of speleothem that hangs from the ceiling or wall of limestone caves. It is sometimes referred to as dripstone....
forms called flos-ferri ("flowers of iron") from their association with the ore

Ore

An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or crystalline formations of metals suc...
s at the Carthinian iron mines.

type location

Type locality (geology)

In some natural sciences, type locality is the typical or representative location and is typically the first example of a newly discovered or described object....
for aragonite is Molina de Aragón (Guadalajara

Guadalajara (province)

Guadalajara is a Provinces of Spain of central/north-central Spain, in the northern part of the Autonomous communities of Spain of Castile-La Mancha....
, Spain

Spain

Spain or the Kingdom of Spain , is a country located in Southern Europe on the Iberian Peninsula.The Spanish constitution does not establish any official denomination of the country, even though Espa?a , Estado espa?ol and Naci?n espa?ola are used interchangeably....
), 25 km outside Aragon

Aragon

Aragon is an autonomous communities of Spain of Spain. Located in northeastern Spain, the region comprises three provinces of Spain from north to south: Huesca , Zaragoza , and Teruel ....
.

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Encyclopedia

Aragonite is a carbonate mineral, one of the two common, naturally occurring polymorphs

Polymorphism (materials science)

Calcium carbonate

Calcium

Carbon

Oxygen

Mineral

Calcite

Crystal twinning

Stalactite

Ore

Occurrence

The type location

Type locality (geology)

Guadalajara (province)

Guadalajara is a Provinces of Spain of central/north-central Spain, in the northern part of the Autonomous communities of Spain of Castile-La Mancha....
, Spain

Spain

Aragon

Aragon is an autonomous communities of Spain of Spain. Located in northeastern Spain, the region comprises three provinces of Spain from north to south: Huesca , Zaragoza , and Teruel ....
. An aragonite cave, the Ochtinská Aragonite Cave

Ochtinská Aragonite Cave

Ochtinsk? Aragonite Cave is a unique aragonite cave situated in southern Slovakia, near Ro?nava. Although only 300 m long, it is famous for its rare aragonite filling....
, is situated in Slovakia

Slovakia

Slovakia . It was amended in September 1998 to allow direct election of the president and again in February 2001 due to EU admission requirements....
. In the USA, aragonite in the form of stalactite

Stalactite

A stalactite is a type of speleothem that hangs from the ceiling or wall of limestone caves. It is sometimes referred to as dripstone....
s and "cave flowers" (anthodite

Anthodite

Anthodites are speleothems composed of long needle-like crystals situated in clusters which radiate outward from a common base. The "needles" may be quill-like or feathery....
) is known from Carlsbad Caverns and other caves. Massive deposits of oolitic

Oolite

Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Ancient Greek word ?oion for egg ....
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 coral

Coral

Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....
s (Scleractinia

Scleractinia

Scleractinia, also called Stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton....
). 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

Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
shells of some extinct ammonite

Ammonite

Ammonites are an Extinction group of marine animals of the Subclass Ammonoidea in the class Cephalopoda, phylum Mollusca. They are excellent index fossils, and it is often possible to link the rock layer in which they are found to specific Geologic time scale....
s forms an iridescent material called ammolite

Ammolite

Ammolite is a rare and valuable opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of the United States and Canada....
. Ammolite is primarily aragonite with impurities that make it iridescent and valuable as a gemstone

Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
.

Physical properties

Aragonite is thermodynamically

Thermodynamics

In physics, thermodynamics is the study of the conversion of heat energy into different forms of energy ; different energy conversions into heat energy; and its relation to macroscopic variables such as temperature, pressure, and volume....
unstable at standard temperature and pressure, and tends to alter to calcite

Calcite

Calcite is a Carbonate minerals and the most stable Polymorphism of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite....
on scales of 10⁷ to 10⁸ years. The young age of the California blueschist

Blueschist

Blueschist is a Rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius....
s has been famously demonstrated by the finding therein of aragonite not yet reverted to calcite. The mineral vaterite

Vaterite

Vaterite is a mineral, a polymorphism of calcium carbonate. It was named after the German mineralogist Heinrich Vater. It is also known as mu-calcium carbonate and has a JCPDS number of 13-192....
, 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.

Aragonite

Occurrence

Physical properties

See also

External links