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Spinel is found as a metamorphic mineral in metamorphosed limestones and silica-poor mudstones. [9] It also occurs as a primary mineral in rare mafic igneous rocks; in these igneous rocks, the magmas are relatively deficient in alkalis relative to aluminium, and aluminium oxide may form as the mineral corundum or may combine with magnesia to ...
Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites, while the other half of the B cations occupy tetrahedral sites. 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.
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 structure. Trivalent iron may also substitute for the aluminium.
The first World Championship Grand Prix was held in 1950 at Silverstone; since then 77 circuits in total have hosted a Grand Prix.A lot of classic (older) circuits have hosted Grands Prix using different configurations throughout their history: Nürburgring, Spa-Francorchamps, Monza, etc. Taking Nürburgring as an example, the first World Championship race there used the 22.835 km (14.189 mi ...
Some foods have always been common in every continent, such as many seafood and plants. Examples of these are honey, ants, mussels, crabs and coconuts. Nikolai Vavilov initially identified the centers of origin for eight crop plants, subdividing them further into twelve groups in 1935.
It is a small to medium-sized tree growing to 7–25 m tall. The leaves are narrow obovate, 20–40 cm in length and 10–20 cm in width. Fruit produced as mentioned earlier, is otherwise aptly known as the Box Fruit, due to distinct square like diagonals jutting out from the cross section of the fruit, given its semi spherical shape form from stem altering to a subpyramidal shape at its base.
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. [4] [5] As such, it is the only gemstone to have been initially identified from a faceted stone.
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.