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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]
Crystal structure of spinel. The space group for a spinel group mineral may be Fd 3 m (the same as for diamond), but in some cases (such as spinel itself, MgAl 2 O 4, beyond 452.6 K [10]) it is actually the tetrahedral F 4 3m. [11] [12] [13] [14]
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
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 ...
In 1838, in the inventory of crown items, the stone under the cross was called a “large ruby”, and in the inventory of 1865 it was already listed as “an irregularly shaped spinel ruby, worth 100,000 rubles”. [15] Since 1967, the crown, and along with it the historical spinel, has been an exhibit of the Diamond Fund.
The spinel is one of the oldest gems in the Crown Jewels of the United Kingdom, with a history dating back to the mid-14th century. According to a legend originating from the 1760s, the stone has been in the possession of the English and later British monarchy since it was given in 1367 by the Spanish king Peter of Castile to the then Prince of ...
Gahnite, ZnAl 2 O 4, is a rare mineral belonging to the spinel group. It forms octahedral crystals which may be green, blue, yellow, brown or grey. It often forms as an alteration product of sphalerite in altered massive sulphide deposits such as at Broken Hill, Australia.
Crystal system: Isometric: Crystal class: Hexoctahedral (m 3 m) H-M symbol: (4/m 3 2/m) Space group: Fd 3 m (no. 227) Unit cell: a = 8.457 Å; Z = 8: Identification; Color: Black to brownish black: Crystal habit: Disseminated to massive, rarely as octahedral crystals: Twinning: Spinel law, flattened on {111} or lamellar: Cleavage {111 ...