Zircon

Information about Zircon

For the spy satellite of this codename see Zircon (satellite).

This article is about the natural mineral Zircon. For the chemically different synthetic diamond substitute, see Cubic zirconium.

Zircon
Zircon crystal from Tocantins, Brazil
General
Category	Mineral
Chemical formula	zirconium silicate ZrSiO₄
Identification
Color	brown, red, yellow, green, black, and colorless
Crystal habit	dipyramidal prismatic
Crystal system	Tetragonal; 4/m 2/m 2/m
Cleavage	indistinct, two directions
Fracture	Subconchoidal to uneven - brittle
Mohs Scale hardness	7.5
Luster	Adamantine
Refractive index	nω=1.967 - 2.015 nε=1.920 - 1.960
Birefringence	δ=0.047 - 0.055
Streak	White
Specific gravity	4.6–4.7
Fusibility	Infusible
Solubility	Insoluble
Other Characteristics	Fluorescent and radioactive

Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is Zr Si O₄. Hafnium is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal class. The natural color of zircon varies between colorless, yellow-golden, red, brown, and green. Colorless specimens that show gem quality are a popular substitute for diamond; these specimens are also known as "Matura diamond". It is not to be confused with cubic zirconia, a synthetic substance with a completely different chemical composition.

The name either derives from the Arabic word zarqun, meaning vermilion, or from the Persian zargun, meaning golden-colored. These words are corrupted into "jargoon", a term applied to light-colored zircons. Yellow zircon is called hyacinth, from a word of East Indian origin; in the Middle Ages all yellow stones of East Indian origin were called hyacinth, but today this term is restricted to the yellow zircons.

Zircon is regarded as the traditional birthstone for December.

Properties

Optical microscope photograph; the length of the crystal is about 250 µm.

Zircon is a remarkable mineral, if only for its almost ubiquitous presence in the crust of Earth. It is found in igneous rocks (as primary crystallization products), in metamorphic rocks and in sedimentary rocks (as detrital grains). Large zircon crystals are seldom abundant. Their average size, e.g. in granite rocks, is about 100–300 µm, but they can also grow to sizes of several centimeters, especially in pegmatites.

Owing to their uranium and thorium content, some zircons may undergo metamictization. This partially disrupts the crystal structure and explains the highly variable properties of zircon.

Zircon is a common accessory mineral and found worldwide. Noted occurrences include: in the Ural Mountains; Trentino, Monte Somma; and Vesuvius, Italy; Arendal, Norway; Sri Lanka, India; Thailand; Ratanakiri, Cambodia; at the Kimberley mines, Republic of South Africa; Madagascar; and in Canada in Renfrew County, Ontario, and Grenville, Quebec. In the United States: Litchfield, Maine; Chesterfield, Massachusetts; in Essex, Orange, and St. Lawrence Counties, New York; Henderson County, North Carolina; the Pikes Peak district of Colorado; and Llano County, Texas.

Thorite (ThSiO₄) is an isostructural related mineral.

Zircon can come in red, brown, yellow, green, black, or colorless. The color of zircons below gem quality can be changed by heat treatment. Depending on the amount of heat applied, colorless, blue, and golden-yellow zircons can be made.

Uses

Zircon dust

Zircons are commercially mined for the metal zirconium, and are used for abrasive and insulating purposes. It is the source of zirconium oxide, one of the most refractory materials known. Crucibles of ZrO are used to fuse platinum at temperatures in excess of 1755 ^oC. Zirconium metal is used in nuclear reactors due to its neutron absorption properties. Large specimens are appreciated as gemstones, owing to their high refractive index (zircon has a refractive index of around 1.95, diamond around 2.4).

Occurrence

Zircon is a common accessory to trace mineral constituent of most granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constituent of most sands. Zircon is rare within mafic rocks and very rare within ultramafic rocks aside from a group of ultrapotassic intrusive rocks such as kimberlites, carbonatites and lamprophyre where zircon can occasionally be found as a trace mineral owing to the unusual magma genesis of these rocks.

Zircon forms economic concentrations within heavy mineral sands ore deposits, within certain pegmatites and within some rare alkaline volcanic rocks, for example the Toongi Trachyte, Dubbo, New South Wales Australia^[1] in association with the zirconium-hafnium minerals eudiyalite and armstrongite.

Zircons and the age of Earth

World production trend of zirconium mineral concentrates

The pervasive occurrence of zircon has become more important since the discovery of radiometric dating. Zircons contain amounts of uranium and thorium (from 10 ppm up to 1 wt%) and can be dated using modern analytical techniques. Since zircons can survive geologic processes like erosion, transport, even high-grade metamorphism, they are used as protolith indicators.

The oldest minerals found so far are zircons from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, with an age of 4.404 billion years,^[2] interpreted to be the age of crystallization. These zircons might not only be the oldest minerals on earth, they also show another interesting feature. Their oxygen isotopic composition has been interpreted to indicate that more than 4.4 billion years ago there was already water on the surface of the Earth. This spectacular interpretation has been published in top scientific journals, but is the subject of debate. Perhaps the oxygen isotopes and other compositional features (the rare earth elements) record more recent hydrothermal alteration of the zircons rather than the composition of the magma at the time of their original crystallization.

References

1. ^ Dubbo Zirconia Project Fact Sheet June 2007 (06/2007). Retrieved on 2007-09-10.
2. ^ [1]

Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
Geochemistry of old zircons
Mineral galleries
Webmineral
Mindat

Zircon was the codename for a British signals intelligence satellite, intended to be launched in 1988, before being cancelled.

During the Cold War, Britain's GCHQ was heavily reliant on America's National Security Agency (NSA) for communications interception from space.
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Cubic zirconia (or CZ), the cubic crystalline form of zirconium dioxide (ZrO₂), is a mineral that is widely synthesized for use as a diamond simulant.
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Motto
Ordem e Progresso (Portuguese)
"Order and Progress"
Anthem
Hino Nacional Brasileiro
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A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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Zirconium (IPA: /zəˈkəʊniəm, ˌzɛːˈkəʊniəm, zɜːɹ'kəʊniəm) is a chemical element that has the symbol Zr and has the atomic number 40.
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silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate ("fluorosilicate"), [SiF₆]²⁻
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habit of crystals.

The many terms used by mineralogists to describe crystal habits are useful in communicating what specimens of a particular mineral often look like. Recognizing numerous habits helps a mineralogist to identify a large number of minerals.
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A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups.
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tetragonal crystal system is one of the 7 lattice point groups. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (a by a) and height (c
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Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types:

Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes.

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fracture is the (local) separation of a body into two, or more, pieces under the action of stress.

The word fracture is often applied to bones of living creatures, or to crystals or crystalline materials, such as gemstones or metal.
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The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in
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For other senses of this word, see lustre.

Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock, or mineral.
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The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.
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Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals or boron nitride, depending on the polarization of
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The streak (also called powder color) of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a
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This article requires authentication or verification by an expert.
Please assist in recruiting an expert or [ improve this article] yourself. See the talk page for details. This article has been tagged since November 2006.
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Fusibility is the ease with which a material will melt. Materials such as solder require a low melting point so that when heat is applied to a joint, the solder will melt before the materials being soldered melt, i.e. high fusibility.
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Solubility is a physical property referring to the ability for a given substance, the solute, to dissolve in a solvent.^[1] It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution.
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Fluorescence is a luminescence that is mostly found as an optical phenomenon in cold bodies, in which the molecular absorption of a photon triggers the emission of another photon with a longer wavelength.
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Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. This decay, or loss of energy, results in an atom of one type, called the parent nuclide
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The silicate minerals make up the largest and most important class of rock-forming minerals. They are classified based on the structure of their silicate ion group.

Subclasses:

Nesosilicates or Isosilicates

Nesosilicates (or orthosilicates
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Silicon (IPA: /ˈsɪlɪkən/ or /ˈsɪlɪˌkɑn/, Latin: silicium
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol⁻¹
2nd: 3388.3 kJmol⁻¹
3rd: 5300.5 kJmol⁻¹

Atomic radius 60 pm
Atomic radius (calc.
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Hafnium (IPA: /ˈhæfniəm/) is a chemical element that has the symbol Hf and atomic number 72. A lustrous, silvery gray tetravalent transition metal, hafnium resembles zirconium chemically and it is found in
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Zircon

Information about Zircon

Properties

Uses

Occurrence

Zircons and the age of Earth

See also

Further reading

References

Nesosilicates or Isosilicates