The English name for spinel is Spinel, which is derived from the Greek word "Spark" and means "natural crystal of red or orange color". Another argument is that it may come from the Latin word "Spinella", which means "thorns."
The chemical formula is MgAl2O4
Crystal system: isometric crystal system
Refractive index: 1.715-1.830
Hardness: 8
Density: 3.58-4.62 g/cm3
Origin: Henan, Hebei, Fujian, Xinjiang, Yunnan, Myanmar, Sri Lanka, Thailand, and China
Spinel is a family of minerals formed in the natural world by the infiltration of molten magma into impure limestone or dolomite by contact metamorphism. Some appear in the basic magmatic rocks of aluminum-rich. Gem-quality spinel is mainly referred to as magnesium-aluminum spinel, which is a magnesium-aluminum oxide. The crystal form is a polyhedron of octahedron and octahedron and rhombohedral dodecahedron. The colors are colorful, and there are colorless, pink, red, purple, light purple, blue purple, blue, yellow, brown and so on. The varieties of spinel are classified according to color, and are red, orange, blue, and blue spinel. The glass is shiny and transparent. Shell-shaped fracture. Light red and red spinels emit red fluorescence under long- and short-wave ultraviolet light.
The difference between spinel and similar gemstones and artificial spinels. The red spinel is very similar to the ruby. The difference is that the ruby ​​has dichroism, uneven color, and has a silky inclusion. Spinel is a homogeneous body, has no dichroism, uniform color, and the solid inclusion body is octahedron. Blue, gray-blue, blue-violet, green spinel and sapphire are easy to mix, the difference is: sapphire dichroism is obvious, the ribbon is straight, there are silky inclusions and twin faces. The density, refractive index, and polarizing properties of the two gemstones are different. The artificial spinel is rich in color, uniform, with few inclusions, and occasionally has a curved growth line with a high refractive index of about 1.727. The red artificial spinel is multi-colored like ruby ​​red, and the blue spinel is more brilliant blue. Natural spinels can also be distinguished from artificial spinels based on the characteristics of the inner inclusions.
Evaluation and purchase of spinel. Color, transparency and weight are the basis for the evaluation and purchase of spinel. Spinel has a variety of colors, usually contains more inclusions, layered distribution, and good transparency. The red spinel is the most popular, bright red, high transparency, and its weight is its best. Spinels with a star effect are also more expensive. Crimson, red, brilliant blue, and green spinels are also preferred.
Spinel has been a precious gem since ancient times. Because of its beauty and scarcity, it is also one of the most fascinating gemstones in the world. Because of its beautiful color, it has been mistaken for ruby ​​since ancient times. The world's most legendary and fascinating 361-carat "Timur Ruby" and the 1660-year-old "Black Prince's Ruby" (170 ft.) ) It was not until the modern times that they were all identified as red spinels. The ruby ​​top used in the Qing Dynasty royal family seal and the one-piece official hat is almost entirely made of red spinel, and no real ruby ​​products have been seen. The world's largest and most beautiful red velvet spinel, weighing 398.72 carats, was purchased by the Russian special envoy in 1676 in Beijing, China with 2,672 gold coins, and is now in the Moscow diamond library in Russia.
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