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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
Actinolite. Nephrite (var.); Adamite; Aegirine; Afghanite; Agrellite; Algodonite; Alunite; Amblygonite; Analcime; Anatase; Andalusite. Chiastolite; Andesine ...
The gemstone at the front of the Imperial State Crown. The Black Prince's Ruby is a large, irregular cabochon red spinel weighing 170 carats (34 g) set in the cross pattée above the Cullinan II diamond at the front of the Imperial State Crown of the United Kingdom. [1]
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.
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 ...
Taaffeite (/ ˈ t ɑː f aɪ t /; BeMgAl 4 O 8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland.