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Polyhedral representation of spinel MgAl 2 O 4. Spinel (/ s p ɪ ˈ n ɛ l, ˈ s p ɪ n əl / [7]) is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula MgAl 2 O 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]
The mineral ceylonite has the chemical composition of (Mg, Fe 2+) Al 2 O 4, putting it into a group of minerals known as the spinel group, or the oxide spinels. The oxide spinels have a formula of the model [A][B] 2 O 4; where [A] is commonly Fe 2+, Mg 2+, or Mn 2+, and [B] is Fe 3+, Al 3+, or Cr 3+. It is an iron-rich variety of the spinel ...
[4] [5] As such, it is the only gemstone to have been initially identified from a faceted stone. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel . For many years afterwards, it was known only in a few samples, and it is still one of the rarest gemstone minerals in the world.
The mineral spinel MgAl 2 O 4 has a normal spinel structure. In a normal spinel structure, the ions are in the following positions, where i, j, and k are arbitrary integers and δ, ε, and ζ are small real numbers (note that the unit cell can be chosen differently, giving different coordinates): [16]
Pages in category "Spinel gemstones" The following 6 pages are in this category, out of 6 total. This list may not reflect recent changes. ...
Spinel gemstones (1 C, 6 P) Pages in category "Spinel group" The following 19 pages are in this category, out of 19 total. This list may not reflect recent changes. ...
[2] [3] Hercynite is a spinel of regular symmetry and normal cation distribution, but some disorder occurs in its structure. It consists of ferrous (Fe 2+) ions and aluminium ions (Al 3+); however some ferric ions (Fe 3+) may be located in the structure of hercynite. [5] Melting point of this mineral is inbetween 1,692–1,767 °C (3,078 ...
Galaxite, also known as 'mangan-spinel' is an isometric mineral belonging to the spinel group of oxides with the ideal chemical formula Mn 2+ Al 2 O 4. [5] Galaxite is the manganese (Mn) rich endmember of the aluminium (Al) series of the spinel group. Divalent iron (Fe) and magnesium (Mg) readily substitute for the manganese in the crystal ...