spinel


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spinel,

magnesium aluminum oxide, MgAl2O4, a mineral crystallizing in the isometric system, usually as octahedrons. It occurs as an accessory mineral in basic igneous rocks, in aluminum-rich metamorphic rocks, and in contact-metamorphosed limestones. Common spinel usually ranges in color from dark green to brown or black, but transparent red, blue, and green varieties are found and are used as gemstones; Myanmar and Sri Lanka are the principal producing countries. Much gem-quality spinel is now produced synthetically.

spinel

[spə′nel]
(mineralogy)
MgAl2O4 A colorless, purplish-red, greenish, yellow, or black mineral, usually forming octahedral crystals, and characterized by great hardness; used as a gemstone.
A group of minerals of general formula AB2O4, where A is magnesium, ferrous iron, zinc, or manganese, or a combination of them, and B is aluminum, ferric iron, or chromium.
References in periodicals archive ?
The company is interested in pursuing discussions for the application of Spinel technologies for all branches of the military.
As a reference, pure magnesium aluminate Mg[Al.sub.2][O.sub.4] spinel was prepared using commercially available powders of MgO and boehmite (aluminium oxide hydroxide, AlO(OH)), average grain size < 0.77 [micro]m.
It is also confirmed that the chromium oxides have been reacted with the iron and nickel to form spinels in the form of Nichromite and Chromite.
For the gel, inflection points were found in the weight ratio curve and the heat flow curve in the region of 550[degrees]C to 650[degrees]C, and this phenomenon was estimated to be caused by the phase change of the spinel crystal.
It is known that nanosized spinel ferrites exhibit properties and phenomena that cannot be explained on the basis of the structure and properties of the consolidated substance [1,2].
The team's findings were mentioned in a study titled "High magnesium mobility in ternary spinel chalcogenides" that appeared Friday in the journal (https://www.nature.com/articles/s41467-017-01772-1) Nature Communications.
In [Mn.sup.2+] doped coated Co[Fe.sub.2][O.sub.4] nanoparticles the diffraction peak of the reflection plane (311) assures the cubic spinel phase.
Spinel Li[Ni.sub.0.5][Mn.sub.1.5][O.sub.4] is a promising and attractive cathode material because of its good electrochemical properties and high working potential (~5.0V) [1-3].
At y [greater than or equal to] 0.06, a secondary phase of iron praseodymium oxide (PrFeO3) appears along with the spinel phase.
Other specifications are an octagonal crown set with a faceted synthetic spinel or a faceted sapphire, Roman numerals, polished leaf-shaped second hand, polished sword-shaped hour and minute hands, Sapphire crystal, Black or gray semi-matte alligator skin strap, 18mm double adjustable folding buckle and more.
Kwong Pui Ho (John Ho), Yangon, Myanmar, for assorted Ammolite, chrome tourmaline, hackmanite, thorite and ruby-in-quartz; rough amber, apatite, corundum, gypsum, jadeite, mica, moonstone, pollucite and tourmaline; crystals of spinel and zircon; cabochons of hematite, kyanite, opal and pargasite; and faceted quartz, spinel and tanzanite.