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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 ...
The Spinel of the Great Imperial Crown (Russian: Шпинель Большой императорской короны) or Menshikov Ruby [1] (Russian: Рубин Меншикова) is a historical gemstone, a red spinel which tops the Great Imperial Crown of Russia from the 18th century to the present day.
An example of an inverse spinel is Fe 3 O 4, if the Fe 2+ (A 2+) ions are d 6 high-spin and the Fe 3+ (B 3+) ions are d 5 high-spin. In addition, intermediate cases exist where the cation distribution can be described as (A 1− x B x )[A x ⁄ 2 B 1− x ⁄ 2 ] 2 O 4 , where parentheses () and brackets [] are used to denote tetrahedral and ...
This is a list of minerals which have Wikipedia articles.. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species.
Samarian Spinel, the world's largest spinel; Menshikov Ruby, the world's second largest spinel set on top of the Great Imperial Crown of Russia; Timur Ruby, believed to be a ruby until 1851, hence its name; Black Prince's Ruby, the famous spinel mounted on the Imperial State Crown of the United Kingdom
[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.
It can be represented by the chemical formula of Fe Cr 2 O 4. It is an oxide mineral belonging to the spinel group. The element magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite (Mg Cr 2 O 4). [6] Substitution of the element aluminium can also occur, leading to hercynite (Fe Al 2 O 4). [7]