See Also

Spinel

The spinels are any of a class of mineral Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

s which crystal Crystal

In chemistry [i] and mineralogy [i], a crystal is a solid [i] in which the constituent atom [i]s, molecule [i] ... 

lize in the isometric system with an octahedral habit. The general formula is as 24, with X representing cations occupying tetrahedral sites and Y cations occupying octahedral sites. Divalent, trivalent, and quadrivalent cations can occupy the X and Y sites, and they include Mg Magnesium

Magnesium is the chemical element [i] in the periodic table [i] that has the symbol Mg and atomic number [i] ... 

, Zn Zinc

Zinc is a chemical element [i] in the periodic table [i] that has the symbol Zn and atomic number [i] ... 

, Fe Iron

Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

, Mn Manganese

Manganese is a chemical element [i] in the periodic table [i] that has the symbol Mn and atomic number [i] ... 

, Al Aluminium

Aluminium or aluminum is the chemical element in the periodic table that has the symbol Al ... 

, Cr Chromium

Chromium is a chemical element [i] in the periodic table [i] that has the symbol Cr and atomic number [i] ... 

, Ti Titanium

Titanium is a chemical element [i] in the periodic table [i] that has the symbol Ti and atomic number [i] ... 

, and Si Silicon

Silicon is the chemical element [i] in the periodic table [i] that has the symbol Si and atomic number [i] ... 

. The oxygen anions are arranged in a cubic close-packed structure. In the normal spinel structure, X cations occupy the tetrahedral sites, and Y the octahedral sites.

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Encyclopedia

Spinel
General
CategoryMineral Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

Chemical formula Chemical formula

A chemical formula is a concise way of expressing information about the atom [i]s that constitute a par ... 

MgAl2O4
Identification
Colour Various, red to blue to mauve. Dark green, brown. Black
Crystal habit Crystal habit

In mineralogy [i], shape and size give rise to descriptive terms applied to the typical appearance, or habi... 

 
Cubic, octahedral
Crystal system Crystal structure

In mineralogy [i] and crystallography [i], a crystal structure is a unique arrangement of atoms in a crystal [i] ... 

 
Isometric
Cleavage Absent
Fracture Conchoidal, uneven
Mohs Scale hardness 8.0
Luster Vitreous
Refractive index Transparent to opaque
Pleochroism ?
Streak Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

White
Specific gravity 3.6 - 3.7
Fusibility ?
Solubility ?
Major varieties
See main article


The spinels are any of a class of mineral Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

s which crystal Crystal

In chemistry [i] and mineralogy [i], a crystal is a solid [i] in which the constituent atom [i]s, molecule [i] ... 

lize in the isometric system with an octahedral habit. The general formula is as 24, with X representing cations occupying tetrahedral sites and Y cations occupying octahedral sites. Divalent, trivalent, and quadrivalent cations can occupy the X and Y sites, and they include Mg Magnesium

Magnesium is the chemical element [i] in the periodic table [i] that has the symbol Mg and atomic number [i] ... 

, Zn Zinc

Zinc is a chemical element [i] in the periodic table [i] that has the symbol Zn and atomic number [i] ... 

, Fe Iron

Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

, Mn Manganese

Manganese is a chemical element [i] in the periodic table [i] that has the symbol Mn and atomic number [i] ... 

, Al Aluminium

Aluminium or aluminum is the chemical element in the periodic table that has the symbol Al ... 

, Cr Chromium

Chromium is a chemical element [i] in the periodic table [i] that has the symbol Cr and atomic number [i] ... 

, Ti Titanium

Titanium is a chemical element [i] in the periodic table [i] that has the symbol Ti and atomic number [i] ... 

, and Si Silicon

Silicon is the chemical element [i] in the periodic table [i] that has the symbol Si and atomic number [i] ... 

.

The oxygen anions are arranged in a cubic close-packed structure. In the normal spinel structure, X cations occupy the tetrahedral sites, and Y the octahedral sites. For inverse spinels, half the Y cations occupy the tetrahedral sites, and both X and Y cations occupy the octahedral sites.

Important members of the spinel group include:

  • spinel – MgAl2O4, after which this class of minerals is named
  • gahnite  - ZnAl2O4
  • franklinite Spinel

    The spinels are any of a class of mineral [i]s which crystal [i]lize in the isometric system with an oct ... 

     - 2O4
  • chromite Chromite

    Chromite, iron magnesium chromium oxide:Cr2O4, is an oxide [i] mineral [i] belonging to the spinel [i] g ... 

     - Cr2O4
  • magnetite Magnetite

    Magnetite is a ferrimagnetic [i] mineral [i] with IUPAC [i] name iron(II,III) oxide... 

     - Fe3O4
  • hercynite - FeAl2O4
  • ulvospinel - TiFe2O4
  • ringwoodite - SiMg2O4, an abundant olivine Olivine

    The mineral [i] olivine is a magnesium [i] iron [i] silicate [i] with the formula 2SiO ... 

     polymorph within the Earth's mantle Mantle (geology)

    Earth's mantle is the thick shell of dense rock surrounding the liquid metallic Earth's outer core [i] ... 

     from about 520 to 660 km depth, and a rare mineral in meteorites


True spinel has long been found in the gemstone Gemstone

A gemstone is a mineral [i], rock [i] , or petrified [i] material that when cut or f ... 

-bearing gravel of Sri Lanka Sri Lanka

Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka , is a tropical [i] island nation [i] ... 

 and in limestone Limestone

Limestone is a sedimentary rock [i] composed largely of the mineral [i] calcite [i] . ... 

s of Myanmar Myanmar

Myanmar, officially the Union of Myanmar is the largest country in geographical area in mainland ... 

 and Thailand Thailand

The Kingdom of Thailand is a country in Southeast Asia [i], bordering Laos [i] and Cambodia [i] to the e ... 

.

Spinel usually occurs in isometric crystals, octahedrons, usually twinned. It has an imperfect octahedral cleavage and a conchoidal fracture. Its hardness is 8, its specific gravity is 3.5-4.1 and it is transparent to opaque with a vitreous to dull lustre. It may be colorless, but is usually various shades of red Red

Red is any of a number of similar color [i]s at the lowest frequencies of light [i] discernible by the h ... 

, blue Blue

Blue is any of a number of similar color [i]s. ... 

, green Green

Green is a color [i] with many different shades, all within a wavelength [i] of roughly 520570 nm [i]... 

, yellow Yellow

Yellow is any color [i] of light that stimulates both the red [i] and green [i] cone cells [i] of the retina [i] ... 

, brown or black. There is a unique natural white spinel, now lost, that surfaced briefly in what is now Sri Lanka. Another famous spinel is the Black Prince's Ruby Black Prince's Ruby

The Black Prince's Ruby is actually a bead-shaped spinel [i] weighing roughly 170 carats [i] that ... 

 in the British Crown Jewels Crown Jewels of the United Kingdom

The collective term Crown Jewels denotes the regalia and vestments worn by the sovereign of the United Kingdom [i] ... 

.

The name "spinel" is derived from the Greek  word for spark, in reference to the fiery red color of spinels often used for gems. The transparent red spinels are also called spinel-rubies or balas-rubies and were often confused with actual rubies Ruby

Ruby is a red [i] gemstone [i], a variety of the mineral [i] corundum [i] . ... 

 in ancient times. "Balas" is derived from Balascia, the ancient name for Badakhshan, a region in central Asia Asia

Asia is the largest and most populous continent [i] or region, depending on the definition.... 

 situated in the upper valley of the Kokcha river, one of the principal tributaries of the Oxus river Amu Darya

The Amu Darya, Amudarya .... 

. Yellow spinel is called rubicelle and violet-colored manganese-bearing spinel is called almandine.

Spinel is found as a metamorphic mineral Metamorphic rock

Metamorphic rock is the result of the transformation of a pre-existing rock [i] type, the protol ... 

, and also as a primary mineral in basic rocks, because in such magmas the absence of alkalis prevents the formation of feldspar Feldspar

Feldspar is the name of an important group of rock-forming mineral [i]s which make up perhaps as much as ... 

s and any aluminium oxide present will form corundum Corundum

Corundum is the crystal [i]line form of aluminium oxide [i] and one of the rock [i]-forming mineral [i] ... 

 or combine with magnesia to form spinel. This is why spinel and ruby are often found together.

The spinel structure type is named after the spinel structure Al2MgO4 but is adopted by a range of species which do not necessarily include oxygen. Sn4N4 for example adopts this structure with Sn in both the octahedral and the tetrahedral holes.

See also: List of minerals List of minerals

This is a List of mineral [i]s for which there are Wikipedia articles. ... 


External links