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This realisation, along with the availability of the recently developed oxyhydrogen torch and growing demand for synthetic rubies, led him to design the Verneuil furnace, where finely ground purified alumina and chromium oxide were melted by a flame of at least 2,000 °C (3,630 °F), and recrystallised on a support below the flame, creating a ...
The mineral spinel MgAl 2 O 4 has a normal spinel structure. In a normal spinel structure, the ions are in the following positions, where i, j, and k are arbitrary integers and δ, ε, and ζ are small real numbers (note that the unit cell can be chosen differently, giving different coordinates): [16]
Ringwoodite is polymorphous with forsterite, Mg 2 SiO 4, and has a spinel structure.Spinel group minerals crystallize in the isometric system with an octahedral habit. Olivine is most abundant in the upper mantle, above about 410 km (250 mi); the olivine polymorphs wadsleyite and ringwoodite are thought to dominate the transition zone of the mantle, a zone present from about 410 to 660 km
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]
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 products business is being pursued by two key U.S. manufacturers: "Technology Assessment and Transfer" and the "Surmet Corporation". An extensive NRL review of the literature has indicated clearly that attempts to make high-quality spinel have failed to date because the densification dynamics of spinel are poorly understood.
Detailed view of the recreated great Golden Fleece of king Louis XV of France. Below the 107 carats (21.4 g) spinel Côte de Bretagne hangs the French Blue diamond and the fleece itself, set with hundreds of yellow diamond replicas. The Tavernier Blue was the precursor diamond to the Blue Diamond of the French Crown (aka the French Blue).
It and a smaller 270-carat (54 g) spinel were captured by the Persian King Nadir Shah during his 18th-century conquest of India.. The Samarian spinel has a hole in it. According to a diary entry of the court physician to the Iranian Shah Nasser al-Din Shah Qajar, the King told the physician that the stone once adorned the neck of the biblical golden calf, which the Israelites are said to have ...