Spinel
Mineral or gemstone / From Wikipedia, the free encyclopedia
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For the larger class of minerals, see Spinel group. For the Russian painter, see Joseph Spinel. For the Steven Universe character, see List of Steven Universe characters § Spinel.
Spinel (/spɪˈnɛl, ˈspɪnəl/[7]) is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula MgAl
2O
4 in the cubic crystal system. Its name comes from the Latin word spinella, a diminutive form of spine, in reference to its pointed crystals.[5]
Quick Facts General, Category ...
Spinel | |
---|---|
![]() Small spinel crystal on top of a white calcite from Mogok, Myanmar, measuring 1.5 × 1.1 × 1 cm in size | |
General | |
Category |
|
Formula (repeating unit) | MgAl 2O 4 |
IMA symbol | Spl[1] |
Strunz classification | 4.BB.05 |
Crystal system | Cubic |
Crystal class | Hextetrahedral (43m) H–M symbol: (43m)[2][3][4] |
Space group | F 4 3 m (No. 216) |
Unit cell | a = 8.0898(9) Å; Z = 8 |
Identification | |
Color | Various; red, pink, blue, lavender/violet, dark green, brown, black, colourless |
Crystal habit | Octahedral or flat triangular plates caused by twinning |
Twinning | common |
Cleavage | None |
Fracture | Conchoidal |
Mohs scale hardness | 7.5–8.0 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent to opaque |
Specific gravity | (Depending on the composition) The rare Zn-rich spinel can be as high as 4.40, otherwise it averages from 3.58 to 3.61. |
Optical properties | Isotropic |
Refractive index | 1.719 |
Pleochroism | Absent |
Solubility | None |
Other characteristics | Weak to medium magnetic, sometimes fluorescent (red synthetic yes, natural red sometimes) |
References | [5][6] |
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![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/8/85/MgAl2O4.png/640px-MgAl2O4.png)