Cordierite

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Cordierite

Cordierite (mineralogy

Mineralogy

Mineralogy is an Earth Science focused around the chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization....
) or iolite (gemology

Gemology

Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy....
) is a magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
cyclosilicate

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
. Iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
is almost always present and a solid solution

Solid solution

A solid solution is a solid-phase solution of one or more soluble in a solvent. Such a mixture is considered a solution rather than a Chemical compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single wiktionary:Homogeneous phase ....
exists between Mg-rich cordierite and Fe-rich sekaninaite

Sekaninaite

Sekaninaite is a mineral which has historically been known to occur only in one locality - in Dolni Bory in Moravia. Until 1968 it was mistaken for cordierite....
with a series formula: (Mg

Magnesium

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
)₂Al₃(Si

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
₅AlO

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]]...
₁₈) to (Fe,Mg)₂Al₃(Si₅AlO₁₈). A high temperature polymorph exists, indialite, which is isostructural with beryl

Beryl

The mineral beryl is a beryllium aluminium Silicate minerals#Cyclosilicates with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size....
and has a random distribution of Al in the (Si,Al)₆O₁₈ rings.

Cordierite is named after the French

France

France , officially the French Republic , is a country whose Metropolitan France is located in Western Europe and that also comprises various Overseas departments and territories of France....
geologist

Geologist

For other uses, see Geologist .A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system ....
P.

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Encyclopedia

Cordierite (mineralogy

Mineralogy

Gemology

Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy....
) is a magnesium

Magnesium

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
cyclosilicate

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
. Iron

Iron

Solid solution

Sekaninaite

Sekaninaite is a mineral which has historically been known to occur only in one locality - in Dolni Bory in Moravia. Until 1968 it was mistaken for cordierite....
with a series formula: (Mg

Magnesium

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
)₂Al₃(Si

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
₅AlO

Oxygen

Beryl

France

Geologist

For other uses, see Geologist .A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system ....
P. L. A. Cordier (1777 - 1861).

Occurrence

Cordierite typically occurs in contact or regional metamorphism

Metamorphism

Metamorphism is the solid-state Crystallization of pre-existing Rock due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids....
of argillaceous rocks. It is especially common in hornfels

Hornfels

Hornfels is the group designation for a series of Metamorphism#Contact_metamorphism rocks that have been baked and indurated by the heat of Intrusion igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable....
produced by contact metamorphism of pelitic rocks. Two common metamorphic mineral assemblages include sillimanite

Sillimanite

Sillimanite also called Bucholzite is an alumino-silicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman ....
-cordierite-spinel

Spinel

The spinels are any of a class of minerals of general formulation A2+B23+oxygen42- which crystallise in the cubic crystal system crystal system, with the oxide anions arranged in a cubic close-packing Bravais lattice and the cations A and B occupying some or all of the octahedral molecul...
and cordierite-spinel

Spinel

Plagioclase

Plagioclase is a very important series of Silicate minerals minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series ....
-orthopyroxene. Other associated minerals include garnet

Garnet

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" comes from the Latin language granatus , possibly a reference to the Punica granatum , a plant with red seeds similar in shape, size, and color to some garnet crystals....
(cordierite-garnet

Garnet

Sillimanite

Sillimanite also called Bucholzite is an alumino-silicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman ....
gneiss

Gneiss

Gneiss is a common and widely distributed type of Rock formed by high-grade regional metamorphic rock processes from pre-existing formations that were originally either igneous rock or Sedimentary rock rocks....
es) and anthophyllite

Anthophyllite

Anthophyllite is an amphibole mineral: 7Si8O222, magnesium iron Silicate minerals hydroxide. Anthophyllite is polymorphism with cummingtonite....
. Cordierite also occurs in some granite

Granite

Granite is a common and widely occurring type of Intrusion , felsic, igneous rock rock . Granite has a medium to coarse texture, occasionally with some individual crystals larger than the groundmass forming a rock known as Porphyry ....
s, pegmatite

Pegmatite

Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite"....
s, and norite

Norite

Norite is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite and hypersthene with olivine. Norite is essentially indistinguishable from gabbro without thin section study under the petrographic microscope....
s in gabbroic magmas. Alteration products include mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition....
, chlorite

Chlorite group

The chlorites are a group of Silicate minerals minerals. Chlorites can be described by the following four Solid solution based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn....
, and talc

Talc

Talc is a mineral composed of hydrated magnesium silicate with the chemical formula Hydrogen2Magnesium34 or Magnesium3Silicon4Oxygen102....
. Cordierite occurs in the granite contact zone at Geevor Tin Mine

Geevor Tin Mine

Geevor Tin Mine was a tin Mining in the far south west of Cornwall, between the villages of Pendeen and Trewellard. It was operational between 1909 and 1991 during which time it produced about 50,000 tons of black tin....
in Cornwall

Cornwall

Cornwall , constitutional Duchy and palatine, is a metropolitan and non-metropolitan counties of England of England, United Kingdom, located at the tip of the south-western peninsula of Great Britain....
.

Commercial use

Catalytic converter

A catalytic converter is a device used to reduce the toxicity of emissions from an internal combustion engine. First widely introduced on Mass production automobiles in the United States market for the 1975 model year to comply with tightening United States Environmental Protection Agency regulations on auto exhaust, catalytic converters a...
s are commonly made from ceramic

Ceramic

File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal solid prepared by the action of heat and subsequent cooling....
s containing a large proportion of cordierite. The manufacturing process deliberately aligns the cordierite crystals to make use of the very low thermal expansion seen for one axis. This prevents thermal shock cracking from taking place when the catalytic converter is used.

Gem variety

As the transparent variety iolite, it is often used 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....
. The name "iolite" comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism

Pleochroism

Pleochroism is an optical phenomenon in which mineral grains within a Rock appear to be different colors when observed at different angles under a polarization petrographic microscope....
. It has also been called "water-sapphire" and "Vikings' Compass" (because of its ability to determine the direction of the sun on overcast days). Gem quality iolite varies in color from sapphire

Sapphire

Sapphire refers to gem varieties of the mineral corundum, an aluminium oxide , when it is a color other than red, in which case the gem would instead be a ruby....
blue to blue violet to yellowish gray to light blue as the light angle changes.

Iolite is sometimes used as an inexpensive substitute for sapphire

Sapphire

Sapphire refers to gem varieties of the mineral corundum, an aluminium oxide , when it is a color other than red, in which case the gem would instead be a ruby....
. It has a low price tag because it is much softer than sapphires and is abundantly found in Sri Lanka, India, Burma, Australia's Northern Territory, Namibia, Brazil, Tanzania, Madagascar, Connecticut, and the Yellowknife area of the Northwest Territories of Canada.

Cordierite

Occurrence

Commercial use

Gem variety

See also

External Links