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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]
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]
Ringwoodite is polymorphous with forsterite, Mg 2 SiO 4, and has a spinel structure.Spinel group minerals crystallize in the isometric system with an octahedral habit. Olivine is most abundant in the upper mantle, above about 410 km (250 mi); the olivine polymorphs wadsleyite and ringwoodite are thought to dominate the transition zone of the mantle, a zone present from about 410 to 660 km
This is the case for spinel law twinning on <111>: The spinel structure has a 3-fold rotational symmetry on <111> and spinel is commonly twinned by 2-fold rotation on <111>. [1] The boundary between crystal segments is called a composition surface or, if it is planar, a composition plane. The composition plane is often, though not always ...
Nickel manganese oxides, [1] or nickel manganates, are spinel structure compounds of Nickel, Manganese and Oxygen of the form: Ni (x) Mn (3-x) O (y) [2] [3] Some common forms are Ni 2 MnO 4, NiMn 2 O 4, and Ni 1.5 Mn 1.5 O 4. They are most commonly formulated for use in thin film resistors and thermistors. [4]
Mn 3 O 4 has the spinel structure, where the oxide ions are cubic close packed and the Mn II occupy tetrahedral sites and the Mn III octahedral sites. [3] The structure is distorted due to the Jahn–Teller effect. [3]
Since layered structures and spinel share an oxygen sub-lattice of the cubic close-packed structure, the evolution of layered structure from spinel only necessitates the migration of Mn from 16d octahedral interstices to another, passing through the tetrahedral interim site without the need for oxygen reordering.
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 ...